Shade
Monster Junkie
As an incorporeal creature, it gets a deflection bonus to AC = Cha modifier.
Some other undead traits I'd recommend to increase its survivability:
Death's Grace (Ex): A gray philosopher gains a +1 profane bonus to AC for every 3 Hit Dice it possesses.
Unholy Toughness (Ex): A gray philosopher gains a bonus to its hit points equal to its Charisma modifier x its Hit Dice.
Some other undead traits I'd recommend to increase its survivability:
Death's Grace (Ex): A gray philosopher gains a +1 profane bonus to AC for every 3 Hit Dice it possesses.
Unholy Toughness (Ex): A gray philosopher gains a bonus to its hit points equal to its Charisma modifier x its Hit Dice.