Racial Substitution Levels: Aasimar and Tiefling

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. Conversely, when a substitution level modifies the list of class skills, this change applies to all levels of the class.

Edit: I plan to have racial substitution levels for all planar races before making this into a series of articles for the site. So far, I've only got the githzerai and githyanki posted. Comments and suggestions are welcome.

AASIMAR CLERIC

Not surprisingly, a substantial percentage of aasimar in the planes are priests of celestial powers. They find their upper-planar heritage to be of great use ascending through the hierarchy of the clerical orders.

1st Level - Turn Fiend (Su): You can turn (but not destroy) extraplanar outsiders with the evil subtype as most clerics turn undead. If you turn an extraplanar creature that has 1/2 your own Hit Dice or less, it is banished to its home plane instead. You can use this ability a total number of times per day equal to 3 + your Charisma modifier.
This class feature replaces the standard turn undead ability.

7th Level - Lesser Planar Host (Ex): You attract devoted followers as if you had the Leadership feat. You do not gain a cohort but you do gain followers, all of whom are outsiders with the good subtype (typically humanoids with the celestial or petitioner template). When consulting the Leadership table to determine their number and level, ignore their ECL.
This class feature replaces the ability to prepare or cast the lesser planar ally spell. This spell is removed from your spell list.

11th Level - Planar Host (Ex): Your gain a cohort as if you had the Leadership feat. This cohort is an outsider with the good subtype (typically an archon, deva, eladrin, or guardinal). When consulting the Leadership table to determine its level, take into account its ECL.
This class feature replaces the ability to prepare or cast the planar ally spell. This spell is removed from your spell list.

AASIMAR FAVORED SOUL

Some aasimar feel naturally predisposed to channeling divine magic, and do so without formalized prayer, preparation, and other such rituals. They see this as part of maturing into a true celestial being.

Class Skills: Add Knowledge (religion) and Knowledge (the planes). Remove Jump.

3rd Level - Power's Domain (Ex): Choose one of the domains offered by your deity. You add the 1st-level spell of that domain to your known spells for free. Whenever you would gain access to a new spell level, you add that level's spell from your chosen domain to your known spells for free.
This class feature replaces the standard deity's weapon focus ability, and also the ability to exchange known spells at even-numbered levels.

5th, 10th, and 15th Level - Energy Resistance (Ex): At each of the indicated levels, choose one of your racial energy resistances (acid, cold, or electricity). It is increased from 5 to 15. You cannot choose the same energy type twice.
This class feature is a modification of the standard energy resistance ability.

12th Level - Audience (Sp): You can use contact other plane as a spell-like ability once per week, but only to contact your deity. Your effective caster level is equal to your class level.
This class feature replaces the standard deity's weapon specialization ability.

20th Level - Damage Reduction (Su): You gain damage reduction 10/evil. Your type and subtype become outsider (native, good).
This class feature replaces the standard damage reduction ability.

AASIMAR PALADIN

There is a greater percentage of paladins among the aasimar then there is in any other planar race. They rarely congregate into knightly orders, and most choose to follow their own personal code of conduct, which usually has more to do with defending against the fiends of the Lower Planes then opposing evil in general.

Class Skills: Add Knowledge (the planes). Remove Knowledge (nobility and royalty).

1st Level - Blessed Strike (Su): Once per day, on a successful attack, you can treat any weapon you wield as good-aligned for the purpose of bypassing damage reduction.
At 5th level, and at every five levels thereafter, the you may make one additional blessed strike per day, to a maximum of five times per day at 20th level.
This class feature replaces the standard smite evil ability.

4th Level - Turn Fiend (Su): You can turn (but not destroy) extraplanar outsiders with the evil subtype as a cleric of three levels lower might turn undead. If you turn an extraplanar creature that has 1/2 your own Hit Dice or less, it is banished to its home plane instead. You can use this ability a total number of times per day equal to 3 + your Charisma modifier.
This class feature replaces the standard turn undead ability.

5th Level - Special Mount (Ex): Your special mount has the celestial template applied. However, you cannot magically summon the mount; it comes and goes as you command, but with no supernatural means of transportation, just like a normal mount would.
This class feature is a modification of the standard special mount benefit.

TIEFLING HEXBLADE

It is said that the original hexblade was a tiefling, a great-grandson of Graz'zt. Whether or not this claim holds any truth, no one can deny that many tieflings become effective hexblades, in spite of the uncharismatic nature that stems from their mixed heritage.

1st Level - Hexblade's Curse Focus (Su): Choose one component of your alignment - either chaos, evil, or law. Your curses, including the greater and dire variants, are 50% less effective against creatures of the chosen alignment, and 50% more effective against those of the opposite alignment. For example, if a 1st-level lawful evil tiefling hexblade chooses law as his favored alignment, his curse imposes a -3 penalty to chaotic creatures, a -1 penalty to lawful creatures, and a -2 penalty to creatures neither chaotic nor lawful.
The choice of alignment focus cannot be altered. If your own alignment strays, this ability may be temporarily suspended (until your alignment resets).

4th Level - Fiendish Charisma (Ex): Your Charisma score is treated as 2 points higher for the purpose of setting saving throw DCs against your curses and spells.
This class feature replaces the standard ability to summon a familiar.

10th Level - Cursed Strike (Su): Whenever you score a critical hit, your target must make a Will saving throw as if you had used the hexblade's curse against it. This does not expend one of your daily uses of the hexblade's curse ability.
This class feature replaces the standard 10th-level bonus feat.

TIEFLING ROGUE

By circumstance or by fate, most tieflings are rogues. The common wisdom says that no two are the same, though, and this applies to both rogues and tieflings...

3rd Level - Shot in the Dark (Ex): You deal an additional +1d6 points of damage on all sneak attacks you make under shadowy illumination or in full darkness. You deal 1d6 points less on sneak attacks you make under normal illumination.
This class feature is a modification of the standard sneak attack ability.

10th Level - Special Ability: Agonizing Strike (Ex): You can sneak attack opponents with such precision that your blows cause additional pain. An opponent damaged by one of your sneak attacks must also make a Fortitude save (DC equal to the damage dealt) or be stunned for 1 round (until just before your next action).
This class feature is an additional option for the "special ability" choice that can be made at 10th level and every 3 levels thereafter.

10th Level - Special Ability: See in Darkness (Su). You can see perfectly in darkness of any kind, even that created by spells.
This class feature is an additional option for the "special ability" choice that can be made at 10th level and every 3 levels thereafter.

TIEFLING WARLOCK

Tieflings that choose to develop their supernatural heritage following the path of the warlock usually overcome their reduced sense of self-worth imposed from an early age by the discriminatory attitude of "untainted" mortal races.

1st Level - Fiendish Charisma (Ex): Your Charisma score is treated as 2 points higher for the purpose of setting saving throw DCs against your eldritch blast effects (if any) and your invocations.
This class feature replaces the ability to learn an invocation at 1st level. From this point on, the number of invocations known is one less than the value shown in Table 1-1: The Warlock, pg. 8 of Complete Arcane.

3rd Level - Damage Reduction (Ex): Your hellish heritage is manifested through your resistance to physical attacks. You gain damage reduction 1/silver. It improves by 1 every four levels thereafter.
This class feature is a modification of the standard damage reduction ability.

4th Level: Eldritch Penetration (Ex): You are adept at circumventing the natural resistance to magic of some creatures. If you choose to reduce your eldritch blast damage by 1d6 or more, you can add these dice to your caster level check to bypass the target's spell resistance. You must choose to use this ability before making the ranged touch attack roll.
This class feature replaces the standard deceive item ability.

10th and 20th Level - Energy Resistance (Ex): At 10th level, choose two of your racial energy resistances (cold, electricity, or fire). They are increased from 5 to 10. At 20th level, the third energy resistance is also increased to 10.
This class feature is a modification of the standard energy resistance ability.