Aberrant Bloodline
There is a taint in your blood, one that is alien and bizarre. You tend to think in odd ways, approaching problems from an angle that most would not expect. Over time, this taint manifests itself in your physical form.
Bloodline Arcana:
You are better than most at changing into all manner of shapes, granting a +1 to clevel when using any shape-changing spell.
Aberrant Form (L31):
Your body becomes truly unnatural, causing others to wonder where they should hit you. You become immune to critical hits.
Bonus Bloodline Skill: dungeoneering
Bonus Spells: enlarge person, detect invisibility, tongues, black tentacles, prying eyes, impenetrable veil, phase door, shapechange