Decaying Hex + Cursed ground interaction

when you support a curse with Decaying Hex, and Cursed ground, when an enemy dies within its radius, it hurts the caster for some reason. my lich goes from 9.6k ES to 0 in a matter of seconds on a pack of enemies. i also am unsure, but it could be related to the lich ascendancy where you sacrifice es to empower a spell, as it never did damage to my life, just kept reducing my ES.