Blessed succubus healing itself?

I've played with the Hostile Champions challenge many times before, but on my last run I faced a particulary nasty blessed succubus. It was the hardest fight I've had playing SPD, ever. It hit hard and often, was almost impossible to hit, but even worse, it healed itself! I spent six or seven healing potions fighting it.

Anyway, I had never seen a succubus healing itself like that. Is it normal? Has anyone seen that happen?