Pretty good, but I don't like the capstone. it's flavorful, but due to how common resurrection is, I could see a paladin just suiciding the BBEG, killing him, than dying, their needs to be some way to die while you are .indomitable. Maybe make it like Stance of immortal Fortitude from ToB, but without automatic ending. Also, it removes the threat if death from the game: I find it unlikely that a 20th level character couldn't get in some healing before the ability ended.