he gets some bonuses at epic levels, i recommend to look at this:
http://nwnprc.com/manual/english/content/prestige_classes/68.html

(PRESTIGE CLASS)
The thirst for power drives some people to extreme lengths, regardless of the consequences. Though it is hard to believe that any living being would willingly bond the skin of a living demon to their own, that is exactly what the Acolyte of the Skin is willing to attempt in their pursuit for power.

Through this diabolic act of symbiosis, the Acolyte hopes to gain infernal power, heedless of the possible consequences to their own soul and psyche. For who knows what may happen as the bond between Acolyte and skin grows stronger and the full power of infernal darkness is unleashed.

Hit Die: d4.
Proficiencies: An Acolyte of the Skin does not gain any additional weapon or armor proficiencies.
Skill Points: 2 + Int Modifier.
Primary Saving throw(s): fortitude, will.
Base Attack Bonus: +1/2 levels.

REQUIREMENTS:

Arcane Spellcasting: Able to cast 3rd-level arcane spells.
Skills: Lore (8 ranks).
Alignment: Any non-good.

ABILITIES:

Level
1: Wear Fiend - Grants +1 Natural Armor, +2 Dexterity and Dark Vision.
2: Flame Resistant - The Acolyte gains 20 Fire resistance.
3: Fiendish Glare - The Acolyte's glare can decrease a foe's abilities and even stun weak opponents.
5: Skin Adaptation - Grants +2 Natural Armor, +2 Constitution.
6: Cold Resistant - The Acolyte gains 20 cold resistance.
7: Glare of the Pit - Once per day, the Acolyte's glare can immolate an opponent, dealing 16d6 damage to a single target.
9: Summon Fiend - The Acolyte can summon a Vrock once per day.
10: Symbiosis - The Acolyte's type changes to Outsider. Grants (20/+1) damage reduction. This increases by +1 every 5 Epic levels.

BONUS SPELLS

Every level in Acolyte of the Skin, the character gains new spells per day as if they had also gained a level in their highest arcane caster class. No new spells are learned through this ability, however.

Bonus stats:
11Level : Venom imunity
11,21,30 +2Con
16,26 +2Int