Unalterable

Unalterable [minor] by Iczer

'Nope...didn't affect me then either. you are free to keep trying though.'

The character's very molecules refuse to be changed, asserting and resetting themselves whenever a nasty alteration takes place.
Effectively the character is immune to powers that alter him or his shape. He may not have his powers toyed with (Cannot have his powers drained or negated, but can be mimicked) and his body cannot be altered (immune to petrification and unwanted shapechanging).
The character remains vulnerable to poison, disease and damage; he cannot be modified however.