Racial substitution levels are optional rules originally introduced in the Races of ... product line, which allow you to flavor your class levels based on your character's race.
A substitution level is a level of a given class that you take instead of the level described for the standard class. Essentially, a substitution level grants you an alternative class feature in place of the standard class feature normally gained at that level. Some substitution levels only modify the standard class feature instead of replacing it completely. The only prerequisite for taking a substitution level being of the proper race and class level.
When a substitution level modifies Hit Dice size, this modification applies only to that level, not all levels of the class (unless otherwise specified). Conversely, when a substitution level modifies the list of class skills, this change applies to all levels of the class.
BLADELING FIGHTER
Bladelings are born for melee combat, with their metallic skin and razor-sharp blades sprouting from every available surface. Combined with the nature of their native plane, it's no wonder that the vast majority are warriors.
2nd Level - Rake (Ex): You gain two additional claw attacks when you grapple a foe. Normally, you can attack with only one natural weapon while grappling, but now you can make two more. These rake attacks are not subject to the usual -4 penalty for attacking with a natural weapon in a grapple.
This class feature replaces the standard 2nd-level bonus feat.
4th Level - Razor Specialization (Ex): When using your razor storm special attack, you deal 2 additional points of damage, and the saving throw DC is increased by +1.
This class feature replaces the standard 4th-level bonus feat.
8th Level - Augmented Critical (claw) (Ex): Your claw attacks deal triple damage on successful critical hits.
This class feature replaces the standard 8th-level bonus feat.
BLADELING MONK
There are no serene monasteries on Acheron where contemplative bladelings develop their chi. Most bladeling monks are lawful and evil worshipers of Hriste, the Gray Whisper, performing ritual sacrifices regularly. Despite their orderliness, they move and fight in a decidedly bestial manner, emulating feline predators.
1st Level - DR Bonus (Ex): Instead of applying your Wisdom modifier to Armor Class, you add it to your damage reduction. So, if you have Wis 16, your damage reduction would be DR 8/bludgeoning. You still apply the level-based bonus to Armor Class.
This class feature is a modification of the standard AC Bonus ability.
1st Level - Flurry of Claws (Ex): Your Flurry of Blows and Ki Strike abilities apply to claw attacks, not unarmed attacks. This allows you to make more than 2 claw attacks per round, which you wouldn't normally be able to do.
Your claw damage scales with level, as shown in the unarmed damage column in Table: The Monk. However, you cannot use your claw attacks to deal nonlethal damage.
This class feature is a modification of the standard Flurry of Blows, Ki Strike, and Unarmed Strike abilities.
3rd Level - Pounce (Ex): When you charge a foe, you can follow with a full-attack action, even though you already moved. If you have the rake ability (see Bladeling Fighter above), you can make your 2 rake attacks as part of this full attack.
This class feature replaces the standard Slow Fall 20 ft. ability. later, when you gain Slow Fall at higher levels, its benefit is 20 ft. less than listed.
15th Level - Rend (Ex): If you hit with two or more claw attacks, you latch onto your foe's body and expertly tear the flesh. This attack automatically deals an extra amount of damage equal to 2 x your base claw damage plus 1.5 x your Strength modifier. However, this exhausts all your remaining attacks for the round, if any.
This class feature replaces the standard Quivering Palm ability.
BLADELING WARMAGE
In bladeling society, primary spellcasters are warmages, not sorcerers or wizards. In fact, the appeal of a profession which grants both destructive spellcasting and physical combat prowess is so great that most bladelings would chose it, were it not for the fact that the warmage trade is a carefully guarded secret, taught only to those who prove talented and determined enough.
Armor/Weapon Proficiency: You are proficient with all simple weapons, but not with any kind of armor or shield.
Class Skills: Add Knowledge (the planes) and Sense Motive.
1st Level - Clawed Mage (Ex): Since you eschew armor, you can afford to neglect your defensive casting abilities and focus almost exclusively on offense. Your base attack bonus progression improves to 3/4 x level (instead of 1/2 x level), not just for this level but for every warmage level.
This class feature replaces the standard Armored Mage (light) and Armored Mage (medium) abilities gained at 1st and 8th level.
3rd, 6th, 11th, and 16th Level - Advanced Learning (Ex): In addition to evocations from the wizard spell list, you can also select magic fang (1st-level spell), barkskin (2nd), chill metal (2nd), heat metal (2nd), greater magic fang (3rd), or stoneskin (5th).
GENASI CLERIC
Almost all genasi priests revere a power of the elements, sometimes a true deity like Akadi or Kossuth, and sometimes an Archomental like Cryonax, Sunnis, or Yan-C-Bin. Their faith is usually a matter of purely personal devotion, and not one that actively seeks converts.
1st Level - Element Specialization (Ex): Your caster level for spells with the energy descriptor matching your genasi variety is increased by one. However, you are unable to cast spells with the opposite energy descriptor (as air is to earth, and fire to both cold and water).
This is an optional class feature; it does not replace any of the standard cleric abilities.
1st Level - Domain Focus (Ex): When you cast a spell from your elemental domain, your effective caster level is increased by +1, as is the saving throw DC against the spell.
This class feature replaces the ability to select a second clerical domain. Your single domain must be the elemental domain matching your genasi variety.
1st Level - Turn Elements (Ex): You have a +4 bonus on turning checks and turning damage checks to turn or destroy creatures of your opposing elemental subtype (as air is to earth, and fire to both cold and water).
This class feature replaces the standard turn undead ability. To select it, you must have access to the elemental clerical domain matching your genasi variety.
GENASI DRUID
Genasi druids are not widely known in the planes, but this is mostly due to the fact that they rarely leave their elemental realms, and their concerns have little to do with those of beings native to the Outer or Material planes. Even those whose connection to the elements is developed gradually find that their druidic practices lead them farther away from animals and plants and toward the purer, baser entities.
Class Skills: Add Knowledge (the planes). Remove Handle Animal.
1st Level - Spontaneous Casting (Ex): You can channel stored spell energy into element-related spells that you haven’t prepared ahead of time. You can "lose" a prepared druid spell in order to cast a spell from the clerical domain of Air, Earth, Fire, or Water (depending on your genasi variety) of the same level or lower.
This class feature replaces the standard spontaneous casting ability.
1st Level - Wild Empathy (Ex): You can use wild empathy against animals, elementals, and magical beasts if their Intelligence is 1 or 2 and they are native to the inner plane matching your genasi variety; no penalty is applied. However, if you use wild empathy against animals or magical beasts native to other planes, a -4 penalty is applied to the check.
This class feature is a modification of the standard wild empathy ability.
4th and 13th Level - Energy Resistance (Ex): Your racial energy resistance improves by 5, once at 4th and again at 13th level.
This class feature replaces the standard resist nature's lure (4th level) and a thousand faces (13th) abilities.
15th Level - Body of Element (Ex): Your type changes to elemental, and you gain either the air, earth, fire, or water subtype (depending on your genasi variety). As an elemental, you no longer need to eat, sleep, breathe, or age; you are immune to crirital hits, paralysis, poison, sleep, and stunning. Additionally, you are no longer able to cast spells with the elemental or enegy descriptor opposite to your subtype (as air is to earth, and fire to both cold and water).
This class feature replaces the standard timeless body ability.
16th, 18th, and 20th Level - Wild Shape (Elemental): You become able to use wild shape to change into one type of elemental, paraelemental, or quasielemental (depending on your genasi variety) of a size equal to or smaller than your own. This elemental form is in addition to your normal available wild shapes. In addition to the standard effects of wild shape, you gain all the elemental's extraordinary, supernatural, and spell-like abilities, and all its feats.
You cannot assume elemental form while on a plane with the energy trait opposite to your elemental form's subtype (as air is to earth, and fire to both cold and water).
At 18th level, you can assume the form of an elemental one size larger than your own, and at 20th level, two sizes larger.
This class feature replaces the standard wild shape (elemental) ability.
GENASI FIGHTER
Most genasi who walk the path of the warrior develop a preference for a type of battle ground that accentuates the unique talents provided by their heritage. Flame lords are an exception, though, since fire is equally useful on most battlefields.
4th Level - Air Mastery (Ex): Airborne creatures take a -2 penalty on attack and damage rolls against you. Only an air genasi can select this substitution level.
This class feature replaces the standard 4th-level bonus feat.
4th Level - Burn (Ex): Opponents who take damage from your unarmed attacks or natural weapons take 2 points of fire damage. Only a fire genasi can select this substitution level.
This class feature replaces the standard 4th-level bonus feat.
4th Level - Earth Mastery (Ex): You gain a +1 bonus on attack and damage rolls if both you and your foe are touching the ground. If an opponent is airborne or waterborne, you take a -4 penalty on attack and damage rolls. Only an earth genasi can select this substitution level.
This class feature replaces the standard 4th-level bonus feat.
4th Level - Water Mastery (Ex): You gain a +1 bonus on attack and damage rolls if both you and your foe are touching water. If an opponent is airborne or touching the ground, you take a -4 penalty on attack and damage rolls. Only a water genasi can select this substitution level.
This class feature replaces the standard 4th-level bonus feat.
I think this ability is way too powerful, both for the ability it replaces and the level at which it's granted.
Gaining the feats of the creature you turn into is strange and unprecedented.
Pants of the North!