They have 9th level spells off a nice list; just remember that; the recharge might be a bit much.

Empowered Essence Drain+Enervating Essence Drain+Withering Essence Drain: I am Incorporeal. I use Essence Drain, and then, upon successfully hitting, activate Enervating Essence Drain, thus inflicting 12 Constitution damage and a negative level.

Which is entirely appropriate, I would say.