Cranium Rats Swarm PC WIP

Are there any monster/NPC listings online yet for the lesser, medium, and greater swarms? The only complete listing (including searching other sites) I can find is The Us, a unique spin on the greater swarm.

OK, I rebuilt this from the ground up with the Fiend Folio entry and swarm rules. Here goes...

Cranium Rat Swarm PC
Adapted from Cranium Rat Swarm (Fiend Folio), with some re-wording from The Us ([url]/node/]) and some formatting from Monster Class: Couatl ([url]/node/]) on Planewalker.

Racial Traits:
- STR -8, Dex +6, Con +4, Int -4, Wis +4, Cha +2
- Medium (Face 5ft, Reach 0) Magical Beast (Extraplanar - Outlands, Swarm of Diminutive [Tiny [*2]] Creatures)
- Darkvision 60 ft, Low-light vision
- Base land speed 40, climb 20 (Natural Climbers)
- Natural Armor +1
- Swarm Growth
- Hive Mind, Telepathy
- Swarm Traits, Swarm Attack, Distraction
- Automatic Languages: None (Telepathy)
- Favored Class: Sorcerer.

Alignment: NE, N, NG (rare)

Hit Die: d10 [d8 [*3]]

Class Skills [*4]: *Appraise (Int), Balance (Dex), *Bluff (Cha), Climb (Str), Concentration (Con), *Decipher Script (Int), *Diplomacy (Cha), **Disable Device (Int), *Disguise (Cha), ***Escape Artist (Dex), **Forgery (Int), *Gather Information (Cha), *Hide (Dex), *Intimidate (Cha), *Knowledge (all, taken individually) (Int), Listen (Wis), *Move Silently (Dex), **Open Lock (Dex), *Profession (ie Spy) (Wis), *Search (Int), Sense Motive (Wis), **Sleight Of Hand (Dex), *Spellcraft (Int), Spot (Wis), **Use Magic Device (Cha)

Recommended Feats (from Fiend Folio descriptions): Alertness, Blind-Fight, Combat Casting, Greater Spell Focus (Evocation), Improved Initiative, Iron Will, Lightning Reflexes, Spell Focus (Evocation), Spell Penetration

Weapon and Armor Proficiencies: None (see Swarm Attack)

Natural Armor: A Cranium Rat Swarm has a +1 natural armor bonus.

Swarm Growth: Being naturally prolific creatures, a swarm's number of members increases every HD/level. Each dice/level gained adds another 12-13 rats (25 every 2 levels) to the swarm, without changing the overall size of Medium.

Natural Climbers (EX): Cranium Rat Swarms have a +8 racial bonus on Climb checks and can always choose to take 10 on Climb checks, even if rushed or threatened

Hive Mind (Ex): A Cranium Rat Swarm has a hive mind which is susceptible to mind-affecting spells. For purposes of such spells, the swarm is a single creature of the magical beast type.

Telepathy (EX): Cranium Rat "speech" is a jumbled mess of sqeaks and other noises only used to share emotions and other base senses within the swarm. A Cranium Rat Swarm communicates with other intelligent beings by natural Telepathy. The range is limited to 20 ft at 1st level, expands to 40 ft at 4th level, and maxes out at 80 ft at 7th level. [*5]

Swarm Traits (EX): A swarm has no clear front or back and no discernible anatomy, so it is not subject to critical hits or flanking. Cranium Rats are a swarm composed of Diminutive creatures so are immune to all weapon damage [(OR) ... Tiny creatures so take half damage from slashing and piercing weapons [*2]]. Swarms are never staggered or reduced to a dying state by damage, and they cannot be tripped, grappled, or bull rushed. Reducing the swarm to 0 hit points or fewer causes the Cranium Rats to fall unconcious as a standard PC [*6], and damage taken until that point does not reduce it's ability to attack or resist attack.
A swarm is immune to any spell or effect that targets a specific number of creatures (including single-target spells such as disintegrate), with the exception of mind-affecting effects. A Swarm has a -10 penalty on saving throws against spells or effects that affect an area, such as many evocation spells or grenade-like weapons. If the area effect attack does not allow a saving throw, a swarm takes double damage instead.
The Diminutive [Ignore this paragraph if using Tiny sized rats [*2]] cranium rats are susceptible to high winds such as that created by a gust of wind spell. To determine the effect of wind, treat the swarm as one Diminutive creature. Wind effects deal 1d6 points of subdual damage to the swarm per spell level (or Hit Die of the originating creature, in the case of effects such as an air elemental's whirlwind). A swarm rendered unconsious by this subdual damage becomes disorganized and dispersed, and does not re-form until its current hit points exceed its subdual damage.

Swarm Attack (EX): Creatures with the swarm subtype don't make standard melee attacks.Instead, they deal automatic nonmagical damage to any creature whose space they occupy at the end of their move, with no attack roll needed. Swarm attacks are not subject to a miss chance for concealment or cover. Cranium Rats attack damage begins at d6 and increases by d6 every 5 levels thereafter. Damage reduction sufficient to reduce a swarm attack's damage to 0, being incorporeal, and other special abilities usually make a creature immune or resistant to damage from the swarm. Swarms do not threaten creatures in their square, and do not make attacks of opportunity with their swarm attack. However, they Distract foes whose squares they occupy, as described below.

Distraction (Ex): Any nonmindless creature vulnerable to the swarm's damage that begins its turn with a swarm in its square is nauseated for 1 round; a Fortitude save negates the effect (DC 10 + 1/2 swarm level (rounded down) + swarm Con). Spellcasting or concentrating on spells within the area of a swarm requires a Concentration check (DC 20 + spell level). Using skills involving patience and concentration requires a Concentration check (DC 20).

Mind Blast (Su): A Cranium Rat Swarm can project a 60-foot cone of mental anguish similar to an illithid mind blast. Anyone caught in this cone must succeed on a Will save or be stunned for 3d4 rounds (DC 11 + 1/2 swarm level (rounded up)). This ability can be used at will (standard action) once per day at 1st level [*7], increasing in frequency every third level, maxing out at 1/round at 9th level.

Shared Intellect (Ex): Every so often, the combined intellectual capacity of a Cranium Rat Swarm is increased by the number of member brains. Starting at 5th level, and every 6 levels thereafter, a Cranium Rat Swarm gains +2 to Intelligence to reflect this.

Cold Resistance (Ex): As Cranium Rat Swarms become more powerful, they develop a resistance to cold both magical and mundane. They gain Cold Resistance 10 at 7th level, Cold Resistance 20 at 13th level, and Cold Immunity at 19th level.

Spells (Sp): At the levels listed above (beginning at 8th), a Cranium Rat Swarm can cast arcane spells as a sorcerer of the level shown. [*8]

Spell Penetration (Greater) (Ex): A Cranium Rat Swarm eventually becomes naturally adept at breaking through Spell Resistance. At 15th level, they gain Spell Penetration as a bonus feat. If they already have Spell Penetration, then they gain Greater Spell Penetration instead.

Spell Resistance (Ex): Extremely powerful Cranium Rat Swarms gain the ability to shrug off outside magical influence completely. Beginning at 21st level, they gain SR 23 (their level + 2). This increases by +1 for every subsequent level.

Psionic Variant
If you're using Psionics in the campaign, Cranium Rat Swarms manifest powers as a Psion (usually Shaper) rather than cast spells as a Sorceror. They would choose psionic feats instead of magic-related ones, such as the Combat Manifestation feat instead of Combat Casting, Power Penetration instead of Spell Penetration, and Pisonic Focus (Metacreativity) instead of Spell Focus (Evocation). The bonus Spell Penetration (or Greater) becomes Power Penetration (or Greater). Favored class becomes Psion.

Notes:

*1 - No abilities for second level. I thought about delaying something from 1st, but that would mess up my progression. Maybe their Natural Armor +1 could wait until here, or their Distraction isn't effective until here... read everything else before making a decision on this. Also, this chart ignores the artificial 20 level cap put on standard classes, since Cranium Rat Swarms have a progression to 24 HD. Also, compressing this to 20 levels would be more of a mess.

*2 - Every source I have points at standard rats being Tiny, so why are Cranium Rats smaller? Making them Tiny (see Swarm Traits) would make them somewhat vulnerable to weapons and help balance out class over-powering.

*3 - Almost every other Swarm I have seen has the standard monster d8 HD, but the C.R.S. has d10. Another option to tone this class down would be to use the d8.

*4 - All class skills marked with asterisks (*) may not necessarily be class skills, but I thought them fitting (Cranium Rats are manipulative gatherers of knowledge). Some should probably be removed for balance. Unmarked skills are listed in the monster descriptions. ** = assuming opposible thumbs as sometimes depicted. *** = chewing through nets, plants, etc; malleable swarm trait.

*5 - The monster entry doesn't get Telepathy until 12HD, but who wants to play a silent PC that long to have it suddenly thrust on them. 80 ft is probably a bit powerful for 1st level, so I put in a somewhat "realistic" progression.

*6 - Changed slightly from standard swarm rules to balance better as a PC.

*7 - Or once per hour depending on the pace of the campaign.

*8 - Spell progression tweaked a bit down from monster listing, to balance out ability progression per class level. Unless I can work out a balanced way to get them to Sorceror 10 as in the monster listing...

Edit (4/25): fixed formatting with "pre" tag

Hey Clueless, I know you said you had a lot going on right now, but you're the only one I know that's admitted to playing my original version of this. You said you'd have more time to deal with stuff soon, so whenever you do, can you give me some more feedback on this. I'd like to get it settled and set up as a new article.

Also, MakThuumNgatha, where have you gotten off to?

Okay, the conversion to these forums now won't allow the [ pre ] tag, and I can't Edit my post above. Here are my latest workings on this. Be sure to check the end to see what still needs help being fixed.

Cranium Rat Swarm PC
Adapted from "Cranium Rat Swarm" (Fiend Folio), with some re-wording from "The Us" (can't find link now) and some formatting from "Monster Class: Couatl" on Planewalker (/070326/monster-class-couatl).

Level F/A  BAB Fort Ref Wil  Special [note *1]
1     Feat  +1   +2  +2  +0  Swarm Attack 1d6, Telepathy 20 ft,
                             Mind Blast 1/Day (DC 12)
2           +2   +3  +3  +0  Distraction (DC 11+Con)
3     F     +3   +3  +3  +1  Mind Blast 1/Turn
4     Attr. +4   +4  +4  +1  Telepathy 40
5           +5   +4  +4  +1  Int +2
6     F     +6   +5  +5  +2  Swarm 2d6, Mind Blast 1/2 Rounds
7           +7   +5  +5  +2  Cold Resistance 10, Telepathy 80
8     A     +8   +6  +6  +2  +1 Sorcerer Caster Level (1)
9     F     +9   +6  +6  +3  Mind Blast 1/Round
10          +10  +7  +7  +3  +1 Sorcerer Caster Level (2)
11          +11  +7  +7  +3  Swarm 3d6, Int +2
12    FA    +12  +8  +8  +4  +1 Sorcerer Caster Level (3)
13          +13  +8  +8  +4  Cold Resistance 20
14          +14  +9  +9  +4  +1 Sorcerer Caster Level (4)
15    F     +15  +9  +9  +5  Spell Penetration (Greater)
16    A     +16 +10 +10  +5  Swarm 4d6, +1 Sorcerer Caster Level (5)
17          +17 +10 +10  +5  Int +2
18    F     +18 +11 +11  +6  +1 Sorcerer Caster Level (6)
19          +19 +11 +11  +6  Cold Immunity
20    A     +20 +12 +12  +6  +1 Sorcerer Caster Level (7)
21    F     +21 +12 +12  +7  Swarm 5d6, SR 23 (level+2)
22          +22 +13 +13  +7  +1 Sorcerer Caster Level (8)
23          +23 +13 +13  +7  Int +2
24    FA    +24 +14 +14  +8  +1 Sorcerer Caster Level (9)

Racial Traits:
- Str -8, Dex +6, Con +4, Int -4, Wis +4, Cha +2
- Medium (Face 5ft, Reach 0) Magical Beast (Extraplanar-Outlands, Swarm of Tiny [*2] Creatures)
- Darkvision 60 ft, Low-light vision
- Base land speed 40, climb 20 (Natural Climbers)
- Natural Armor +1
- Magical Beast Traits
- Extraplanar Traits (only applies outside their home plane if rule used at all)
- Swarm Traits, Swarm Attack, Distraction
- Swarm Growth
- Hive Mind, Telepathy
- Automatic Languages: None (Telepathy)
- Favored Class: Sorcerer. Levels in any class can be taken, slowing advance of racial class levels, but they usually provide little to no benefit due to racial weapon and armor restrictions and racial caster levels gained naturally.

Alignment: any N; usually NE, N, or LN (NG or CN are very rare and may be seen as enemies by their brethren)

Hit Die: d10 (possibly d8 [*3])

Class Skills [*4]: *Appraise (Int), Balance (Dex), *Bluff (Cha), Climb (Str), Concentration (Con), *Decipher Script (Int), *Diplomacy (Cha), **Disable Device (Int), *Disguise (Cha), ~Escape Artist (Dex), **Forgery (Int), *Gather Information (Cha), *Hide (Dex), *Intimidate (Cha), *Knowledge (all, taken individually) (Int), Listen (Wis), *Move Silently (Dex), **Open Lock (Dex), *Profession (i.e. Spy) (Wis), *Search (Int), Sense Motive (Wis), **Sleight Of Hand (Dex), *Speak Language (-), *Spellcraft (Int), Spot (Wis), **Use Magic Device (Cha)

Skill Points: 2 + Int/Level (quadruple at 1st)

Feats/Attributes: These characters gain Feats and Attribute Points to allocate every third/fourth character level respectively just like standard PCs. This is listed in the table for reference (not accurate if other character levels are taken).

Recommended Feats (from Fiend Folio descriptions): Alertness, Blind-Fight, Combat Casting, Greater Spell Focus (Evocation), Improved Initiative, Iron Will, Lightning Reflexes, Spell Focus (Evocation), Spell Penetration

Weapon and Armor Proficiencies: None (Swarm Attack/Traits used instead); never any gained by taking Class Levels in other classes or Feats either. Equipment not requiring proficiency (rings, etc) has the same number of limited slots as standard PCs (i.e. two rings total, one of other items). Rings can fit on tails, but it’s up to the DM whether to allow other humanoid equipment such as bracers.

Natural Armor: A Cranium Rat Swarm has a +1 natural armor bonus.

Swarm Growth: Being naturally prolific creatures, the swarm's number of members increases every level. Each level gained adds another 12-13 rats (25 per 2 levels) to the swarm, without changing the overall size of Medium. (This has no real impact on game mechanics, until extremely high levels.) [*5]

Natural Climbers (Ex): Cranium Rat Swarms have a +8 racial bonus on Climb checks and can always choose to take 10 on Climb checks, even if rushed or threatened.

Hive Mind (Ex): A Cranium Rat Swarm has a hive mind which is susceptible to mind-affecting spells. For purposes of such spells, the swarm is a single creature of the Magical Beast type.

Telepathy (Ex): Cranium Rat "speech" is a jumbled mess of squeaks and other noises only used to share emotions and other base senses within the swarm. A Cranium Rat Swarm communicates with other intelligent beings by natural Telepathy. The range is limited to 20 ft at 1st level, expands to 40 ft at 4th level, and maxes out at 80 ft at 7th level. [*6]

Magical Beast Traits (Ex): 10-sided Hit Dice. Base attack bonus equal to total Hit Dice (as fighter). Good Fortitude and Reflex saves. Skill points equal to (2 + Int mod) per Hit Die, with quadruple skill points for the first Hit Die. Darkvision out to 60 feet and low-light vision. Proficient with its natural weapons only. Proficient with no armor. Magical beasts eat, sleep, and breathe.

Swarm Traits (Ex): A swarm has no clear front or back and no discernible anatomy, so it is not subject to critical hits or flanking. Cranium Rats are a Medium sized swarm composed of Tiny creatures so take half damage from slashing and piercing weapons. Swarms are never staggered or reduced to a dying state by damage, and they cannot be tripped, grappled, or bull rushed. Reducing the swarm to 0 hit points or fewer causes the Cranium Rats to fall unconscious as a standard PC [*7], and damage taken until that point does not reduce it's ability to attack or resist attack.
A swarm is immune to any spell or effect that targets a specific number of creatures (including single-target spells such as disintegrate), with the exception of mind-affecting effects. A Swarm has a -10 penalty on saving throws against spells or effects that affect an area, such as many evocation spells or grenade-like weapons. If the area effect attack does not allow a saving throw, a swarm takes double damage instead.

Swarm Attack (Ex): Creatures with the swarm subtype don't make standard melee attacks. Instead, they deal automatic non-magical damage to any creature whose space they occupy at the end of their move, with no attack roll needed. Swarm attacks are not subject to a miss chance for concealment or cover. Cranium Rat swarm attack damage begins at d6 and increases by d6 every 5 levels thereafter. Damage Reduction sufficient to reduce a swarm attack's damage to 0, being incorporeal, and other special abilities usually makes a creature immune or resistant to damage from the swarm. Swarms do not threaten creatures in their square and do not make attacks of opportunity with their swarm attack, but they are subject to attacks of opportunity by foes. They may also Distract foes whose squares they occupy, as described below.

Distraction (Ex): Any non-mindless creature vulnerable to the swarm's damage that begins its turn with a swarm in its square is nauseated for 1 round; Fortitude Save negates the effect (DC 10 + swarm Con bonus + 1/2 swarm level, rounded down). Spell-casting or concentrating on spells within the area of a swarm requires a Concentration check (DC 20 + spell level). Using skills involving patience and concentration requires a Concentration check (DC 20).

Mind Blast (Su): A Cranium Rat Swarm can project a 60-foot cone of mental anguish similar to an Illithid mind blast. Anyone caught in this cone must succeed on a Will save or be stunned for 3d4 rounds (DC 11 + 1/2 swarm level, rounded up). This ability can be used at will (standard action) once per day at 1st level [*8], increasing in frequency every third level, maxing out at 1/round at 9th level.

Shared Intellect (Ex): Every so often, the combined intellectual capacity of a Cranium Rat Swarm is increased by the number of member brains. Starting at 5th level and every 6 levels thereafter a Cranium Rat Swarm gains +2 to Intelligence to reflect this.

Cold Resistance (Ex): As Cranium Rat Swarms become more powerful, they develop a resistance to cold both magical and mundane. They gain Cold Resistance 10 at 7th level, Cold Resistance 20 at 13th level, and Cold Immunity at 19th level.

Spells (Sp): At the levels listed above (beginning at 8th), a Cranium Rat Swarm gains an arcane caster level as Sorcerer. If they have no class levels in Sorcerer, they can cast arcane spells as a sorcerer of the level shown in parenthesis. [*9]

Spell Penetration (Greater) (Ex): A Cranium Rat Swarm eventually becomes naturally adept at breaking through Spell Resistance. At 15th level, they gain Spell Penetration as a bonus feat. If they already have purchased Spell Penetration, then they gain Greater Spell Penetration instead.

Spell Resistance (Ex): Extremely powerful Cranium Rat Swarms gain the ability to shrug off outside magical influence completely. Beginning at 21st level, they gain SR 23 (their level + 2). This increases by +1 for every subsequent level.

Psionic Variant:
If you're using Psionics in the campaign, Cranium Rat Swarms manifest powers as a Psion (usually Shaper) rather than cast spells as a Sorcerer. They would choose Psionic feats instead of magic-related ones, such as the Combat Manifestation feat instead of Combat Casting, Power Penetration instead of Spell Penetration, and Psionic Endowment or Psionic Focus (Metacreativity) instead of Spell Focus (Evocation). The bonus Spell Penetration (or Greater) becomes Power Penetration (or Greater). Spell Resistance may be replaced with Power Resistance, if there is a difference in the campaign. Favored class becomes Psion.

Beyond 24th Level: A Cranium Rat Swarm gains no more unique abilities but continues to grow larger, increasing their existing abilities at the rates given. Around this point the number of Cranium Rats has increased so much that the swarm no longer fits inside a single standard 5’ square and may spill into one adjacent square (or more squares given enough numbers). Most swarms split in half and go their separate ways before this, though there are rumors of very rare large gatherings. They may be forcibly split by greater beings, possibly even their own deity or the Lady of Pain if they are causing trouble.

Names: Many as One, The Us, The Collective, Ilsensine's Eyes, Keeper of Secrets

[flavor text goes here]

Notes:

*1 - Attempted to spread special ability progression evenly per level over the 24 Hit Dice given for the Greater Swarm. For example, Distraction isn't effective until 2nd level due to the swarm not yet having enough members. Also, this chart ignores the artificial 20 level cap put on standard classes, since Cranium Rat Swarms have a progression to 24 HD, though they only gain an “Epic” ability of sorts after 20th level. Compressing this to 20 levels would be more of a mess.

*2 - Every source I have points at standard rats being Tiny; why are Cranium Rats listed as smaller (Diminutive) in the Fiend Folio? Even the Greater swarm is listed as having 300 members, the limit in one space for a swarm of Tiny, not even close to the 1500 that a Diminutive swarm can reach. Making them Tiny also would make them not immune to weapons and help balance out class over-powering.
[Diminutive alternate Swarm Traits (Ex): Immune to all weapon damage. Susceptible to high winds such as that created by a gust of wind spell. To determine the effect of wind, treat the swarm as one Diminutive creature. Wind effects deal 1d6 points of subdual damage to the swarm per spell level (or Hit Die of the originating creature, in the case of effects such as an air elemental's whirlwind). A swarm rendered unconscious by this subdual damage becomes disorganized and dispersed, and does not re-form until its current hit points exceed its subdual damage. Other traits are same as swarm of Tiny.]

*3 - Almost every other Swarm that I have seen has d8 HD, but the C.R.S. has d10 being Magical Beasts. Another option to tone this class down would be to use the d8.

*4 - * = All class skills marked with asterisks are only potentially class skills, but I thought them fitting (Cranium Rats are manipulative gatherers of knowledge). Some could probably be removed for balance. Unmarked skills are listed in the monster descriptions and are staying.
** = assuming opposable thumbs and/or prehensile tails as sometimes depicted.
~ = chewing through nets, plants, etc; malleable swarm trait.

*5 - the adjustment from Diminutive to Tiny (like normal rats) means total rats (25 / 2 levels) would not be able to fit inside the 5' square after 24th level. See “Beyond 24th Level” above for more information. Until then, number of rats doesn’t really matter to game mechanics, only for flavor.

*6 - The monster entry doesn't get Telepathy until somewhere between 6 and 12HD, but who wants to play a silent PC that long to have it suddenly thrust on them. 80 ft is probably a bit powerful for 1st level, so I put in a somewhat "realistic" progression. DMs wishing to restrict this further may require character to purchase Speak Language skills to understand and be understood by particular language speakers, though they should give them Common freely to aid in party unity.

*7 - Changed slightly from standard swarm rules to balance better as a PC.

*8 - Or once per hour depending on the pace of the campaign.

*9 - Spell progression tweaked a bit down from monster listing to balance out ability progression per class level, unless I can work out a balanced way to get them to Sorcerer 10 as in the monster listing...

To do:
- flavor text is needed.

Still need help with:
- Overall adjustments +4 now; tweak stat adjustments? Str usually counts for more than other stat adjustments anyway, so balance may be fine.
- Drop Hit Die to d8 since d10 may be too overpowered? Then again, they can never wear armor...
- Pare down the number of Class Skills? Most Rogue ones would likely be the first to eliminate. Or is the number listed not too many? It’s not like they have that many skill points to spend anyway.

I'll start off by saying thank you for taking the time to post a detailed response, as so few people take this class concept seriously enough to even consider it. That said, I am confused about some things, like it seems you are implying the class is both too strong (hit die, Mind Blast power) and also too weak (class ability progression). Personally, I was worried about them being too strong and made every effort to avoid them getting an ECL +x. Also, keep in mind this class is for D&D 3.5, which has a different power scale than 4e from what I've heard. So try and recall how things worked in the former if you've gotten used to playing the latter.

Foremost, I don't really want to totally rebuild this class from the ground up again. A few tweaks here and there are fine as I personally think overall it's in good shape, and I don't want the headache of recalculating every aspect again from scratch like I did when I finally discovered the Fiend Folio entries. Next, I'll take your responses point by point.

re: CR - "The number on this line of the statistics block represents the average level of a party of adventurers for which one creature would make an encounter of moderate difficulty. Assume a party of four fresh characters (full hit points, full spells, and equipment appropriate to their levels). Given reasonable luck, the party should be able to win the encounter with some damage but no casualties."
In other words, CR11 does not equal one level 11 character, but four. Therefore, the Greater Swarm is equal to four level 11 characters, not one. So, this means that class ability progression is fine as it is. Besides, normal PCs only get one, two, sometimes no new/improved class abilities on a given level, similar to the one or two per level given here.

re: Stat adjustments - now we're talking. Like I said, as it is, they have +4 overall, though some of that is maybe countered by the large strength penalty possibly counting for more than the other adjustments, i.e. Half-Orcs get two -2s for their one +2 in Str. Then again, Halflings only get a +2 to Dex for their -2 in Str. However, I am considering changing the adjustment total to +2 overall or even +0 if possible. For one, I think the CRS's high Dex of 17 in the monster entry is due to them mistakenly labeled as Diminutive, as Tiny normal Rats only have only as 15, so that's going down to +4. As for the other +2 to drop... maybe some of their Con bonus as a counter for the high hit dice? This would conflict from what I extracted from the monster entries though, but it still includes a high Str penalty (which may matter more than you think: see below). So, how's this sound?:
Str -8, Dex +4, Con +2, Int -4, Wis +4, Cha +2

re: Telepathy - I thought 20 ft would be sufficient to communicate around the campfire or whatever. Sure, it's a bit short for the battlefield, but I did that for balance. How understandable is the spoken word beyond that range anyway? Maybe it could start at 40 and increase to 80 at 5th level, but that leaves them with it before the monster entry gets it... unless they just mistakenly left it off the Lesser Swarm entry. CRS monster entry never gets 100 ft, by the way.

re: Mage Hand, lifting - I should probably be more explicit in the Weapon restrictions. Something like: "The rats writhing about in the swarm climbing about each other makes usage of even improvised weapons impossible, so Swarm Attack rules are used instead. They have to rely on Mind Blast and spells for missile attacks." Since the Swarm counts as a single Medium creature, they work together and lifting is handled like a size M with that Str. So, remember dumping a very low number into Str may severely hinder what the Swarm can carry about anyway. I only allowed certain magical gear as we don't want them to avoid items all together like some sort of Forsaker. The magical aura generated by an object worn/carried by the swarm encompasses and treats the group as an individual, just like everything else.

re: Mind Blast - I got the idea of scaling frequency from the monster entries where lesser (6HD) gets one every two rounds and the stronger ones get at-will some time before 12 HD. Also, remember that this ability allows a Will save against a not very high DC so it's not like a guaranteed show stopper. I can add a DM note about possibly scaling area of effect and duration instead of frequency though.

re: Psionics, Sorceror - yeah I left that in as an option, but kept the Sorcerer stuff in for those not wanting to play with Psionics. Caster level is drawn straight out of the monster entry and probably doesn't really need a change (except maybe for simplicity). As for those Feats, the CRS is free to use their character level feats to take them, but I see no need to give them away, again as it may be over-powered. They use V and S components to spells, just not the ones humanoids are quite used to, like squeaks and chitters and the swarm writhing about rhythmically.

re: Hit Dice, Saves - I don't know if scaling back that far is necessary, as they are still Magical Beasts after all. Think of this as more a racial class than a standard class. I did think of bumping up the Will saves, but the monster entry doesn't have strong Will (accounting for the Iron Will Feat). So I don't think a drop in HD is needed for that. Maybe they keep their minds a bit open due to their hive mind, so this keeps them from developing a truly high Will.

re: Base Attack Bonus - yep, it's not used in melee but actually it is still used for Ranged Touch Attacks for their Sorcerer spells. Is it a bit high for that? I'd like to leave it alone, as it's part of one of their Racial Templates, hence a part of their Racial Class.

re: Int bonuses - there's a ramp up of Int in the monster entries that can not be accounted for by the normal +1 to one stat every 4th level/HD. The only thing I could figure is that they get an Int boost every few HD to reflect the same in the previous AD&D 2nd edition version. Sure, it's more for flavor than useful, but they do get more skill points too, something the class is sorely lacking otherwise. If you have a nice enough DM to allow retroactive skill point gains for raised Int, all the better.

re: Cold Resistance/Immunity - just part of their racial makeup, like many other extra-planar creatures naturally get similar immunities.

re: Targeted Effect Immunity - yeah, I don't know what they were thinking when they put that in the CRS monster entries, except that killing just one rat doesn't do much. I see what you mean in that they should treat the group as an individual just like everything else.

re: Class Skills - yeah those were just the ones I was thinking about dropping. Guess I put some in due to Bard or Ranger access meaning they weren't just Rogue exclusive. Disable Device, Open Lock, Sleight of Hand were to be done with their nimble little hands and prehensile tails. Disguise was partly a joke referring to the joke theory of the Lady of Pain being a bunch of squirrels under a robe. Hide and Move Silently: sad to see them go, but the former would reflect the fact that swarms can move through spaces as small as the individual member, while the latter especially doesn't make sense with a writhing squeaking mass. Use Magic Device made sense to me because I think they don't gain the Sorcerer class ability to use Arcane items; they're only able to cast Arcane spells. Or does the casting ability allow item use as if you're that class? I do also remember an illustration from 2e of a Cranium Rat holding a magic wand.

(Note to self: Speak Language has to reference that it's used for Telepathy.)

re: Epic Levels - taking another look, I see the only thing new gained there is the Spell Resistance. The other stuff is just extended progression from earlier abilities, which I never believed any class should just suddenly lose when they pass 20th level anyway. I suppose I could find room for those level 21 abilities at 20th and smash other things down a level to make it a standard 20 level class after all. Also, remember anything over 20 levels/HD is free to take Epic Feats as usual.

Finally, sorry again for shooting down some of your suggestions. However, I do greatly appreciate the advice and look forward to more ideas.

Hmm, I was just thinking. One must also take into account that this listing gives out racial abilities as class abilities, unlike a standard PC that gets all their racial abilities right away. So therefore, this entry may not be as on the verge of overpowered as I thought, since it has to account for both race and class abilities. Then again, there is a template and one or two sub-templates applied at first level, which would be equivalent to racial abilities for a standard PC. Yeah, in the end, I think the progression works as it is, with a couple tweaks (stat adjustments, class skills) listed a couple posts above this one, but I just need a play-tester to make sure.

Guess I could always start a play-by-post or join one. Though, if I were the player, I'd try not to exploit any possible loopholes in the design since that's how I roll. I need someone to put it through the wringer. Man I know I could have used some cant there, but I am so out of practice, heh.

Yeah, the monster entries for the swarms can do something like this with the Merge Swarms (Ex) ability. Two Lesser (6HD) can combine into Average (12 HD), and two Average can combine into Greater (24 HD). I purposely left this off since it would add way too much complexity and be too unbalancing to playing this as a single PC with gradually added levels.

I also left off the Swarm Regeneration (Ex) trait, which is not as good as it sounds. Basically, if the bigger swarm's HP is reduced to zero, it becomes a lower category swarm and permanently loses half its hit dice. Lesser Swarms reduced to zero HP are destroyed.

Instead, I give the player a little leeway of having the swarm fall unconscious at zero HP, similar to a standard PC. They die at -10 too, but as PCs the swarm can be Raised as a single creature. This was the best way I could think of balance these aspect for use as a PC.

Note also, that they are free to take Sorcerer levels to gain a Familiar, just like anyone else.

I guess we're going to have to agree to disagree on this one - what I'm proposing seems underpowered to you, but what you have seems too overpowered in some ways to me. One again, I say that I've been too worried about my adaptation actually being too strong, not compared to the monster entry but compared to PC classes of a given level especially the lower levels. Or maybe you're trying to give them a +ECL and start them out at maximum strength. Instead, I was extrapolating down from the 6 HD version to show what a level 1 (+0 ECL), 1 HD character would start out with. Then I set progress points based on the Average and Greater Swarms and filled in between accordingly.

I agree that the monster entry is way low on CR listed. In fact, a PC's level is effectively equal to its number of HD. If a 12 HD Level 12 PC has a CR of 12, then wouldn't a 12 HD Average Swarm played as a PC, with level appropriate magic items, and supported by his companions also have a CR of 12? Maybe I'm trying to think outside the box (and the DMG) too much on this, but this was the assumption I was going by when I tried to balance the progression.

+14 Con in 11-15 levels (that's +7 HP / level, retroactive)?! Does any PC get this much? Maybe with a huge +x ECL. I don't even know where you are pulling this number from, as the monster entry definitely has +4. Unless you only give them d4 HD, in which case this still works out eventually to 8-11 HP per level, which is much better balanced as d10 with +4 Con. I'm going to chalk this up to a typo that was supposed to be +4.

SR 12+level? Again, that's a bit much to start out at first level with unless you are adding ECL. Besides, even the monster entry eventually only gets 2+HD, not 12+HD, and it starts somewhere between 12 and 24 HD. I may be willing to extrapolate this down to 10th level (maybe 13th) and count up from there, as I was of the idea that only somewhat advanced swarms got this, kind of like other classes (namely Monk gets SR at 13th level).

Swarm Damage - so by 20th level gets up to 10d6 automatic damage after taking a Move Action? Even a medium Monk, master of unarmed attack, only gets 2d10 at that level (3 times if they can hit all attacks in a Full Attack action thus haven't moved too much). Sure, Rogues eventually get a +10d6 Sneak Attack, but they are a much more martial class than my entry and Sneak Attacks are not guaranteed.

Bonus Feats - umm, maybe. Count the number of Feats in the Fiend Folio monster entries. There is one for every three HD plus one for the first HD, which is exactly the number of feats a PC gets per character levels. Then again, compare to Monk, and see that Monks have the same number of abilities as my progression over the first couple levels, plus a couple bonus Feats. That class is overpowered though, but I may still add one at 1st or 2nd.

Also again notice that my progression gives out at least one or two new or improved abilities at every level. Compare this to Fighters who, while front loaded, then only get one bonus Feat every other level - with the same HD, BAB (eventually multiple attacks), skill progression, and worse Ref saves.

Caster Level - this is delayed on my entry in order to best reflect the progression per HD from the Fiend Folio monster entry. Remember, even 2nd Edition Cranium Rats couldn't cast spells until the pack got enough members, so keep that in mind as you try to keep with the iconic image. At least I'm not starting them at an Int of 1 with casting as a Wizard like in that version (or even a starting Cha of 1 casting as a Sorcerer), increasing the stat every couple levels. Believe me, I tried working with that mess before, and it wasn't pretty. And, thanks for the comparison to a certain uppity princess (which she wasn't really once you got to know her). Besides, I'm a guy

Strength - do you realize how little carrying capacity that dumping down to a 1 or 2 after ability adjustment gives them? I know this mechanic is usually overlooked by many DMs except in extreme situations, and I would consider this extreme. They can only carry 3 or 6 pounds before being encumbered, so say goodbye all but very few magic items (remember I gave them the ability to use many of these as a standard individual PC) and to carrying spell components. Also, movement would be easily slowed to 30 ft at best, while the encumbrance also imposes a Max Dex cap. So as a player, I'd be strongly inclined to put at least a couple points in this in order to not have to worry later. Also, I am again considering bumping this to -6 as in your version (though every Tiny creature I've seen has a 2 or 3 in Str, even Swarms of them). Also, why doesn't Str modifier affect Swarm Attack damage? I guess the rule uses the fact that multiple units are applying the damage to nullify the strength penalty of each unit?

Telepathy - Close range? You mean 25 ft + 5 ft / 2 levels? That actually works out as less than what I had listed in the long run. I will now probably give 40 ft at level 1 and 80 ft at level 5ish by the way. As for Tongues, yeah, I guess you could go that way, but I was thinking it was more non-lingual communication anyway, where they automatically understand what is being said. I just put in the option of requiring Language skills for DMs who balk at effectively giving a PC free access to any language that happens to be flying about in the area, thus cheapening language limitations on the rest of the party.

Mage Hand - why give them the free ability to manipulate things at range? They can already handle things just fine as a creature of their given strength, which would mean about as much weight as Mage Hand can lift anyway. Besides, they will be able to cast this normally as a 0 level Sorcerer spell anyway whenever they get spells.

Mind Blast - what's wrong with my level 3 entry? You mean that I don't list the DC? The DC advancement is implied already by the ability description below the table. I just listed the increased frequency of usage where appropriate. I guess to be consistent, I should not list the DC at 1st level either, heh.

BAB - the monster doesn't have a ray spell above 1st level, but there's nothing stopping a player from choosing different Spells Known for the PC.

Targeted Effect Immunity - yep, already nixed that idea.

Class Skills - "Abuse" Magic Device, lol. My only reason for allowing this was to let them use rods, etc with higher level spells than they were able to cast. I never really did clearly get how the skill worked, so I guess that point may be moot. Guess I was thrown off by the fact that my first 3e character was a Bard, a casting class that also got UMD. So, I've always kept falling back to the erroneous assumption that even casters need UMD to "Emulate a Class Feature" of a high enough level caster to cast the spell that the item uses.

Epic Levels - yeah, just ignore my rambling there, heh. Suffice it to say that I'm not happy with the way they handled "Epic" Levels in 3e or 3.5, and I was trying to ignore them in the first version. I figured out a way to cut my 24 level progression down to 20 levels after all, so the Epic rules won't matter either way now.

re apology - I was afraid that you might read my response as something other than the humble counterpoints I was trying to make. At least it's my intention to not try to sound like a know-it-all, and I wasn't meaning anything as a personal attack on your views. Once again, I appreciate the extended feedback you take the time to give, but it looks like we're approaching the subject from two very different angles at times.