[Taqwus]

Healing commanders (be they Faerie Queens, Arco priestesses, the one TC immortal, whatever) can't heal undead or lifeless inanimates, if memory serves. Illearth doesn't have any flags that would impair his healing, as far as I can tell.

Never-healing wounds can be healed, but there's a penalty to the die roll for them. Diseases can be healed; until they do, they'll still cause hp loss and potentially more afflictions.