Gruesome Feast

I was fighting a Flesh Golem and took it down as a Tomb Troll Necromancer entered the room. Instead of attacking me, it did this:

With a ravenous glint in his eye, a tomb troll necromancer pounces upon the body of a flesh golem and begins feasting on its abdomen. Within seconds, the golem’s midsection is torn asunder and the troll necromancer looks up from his meal with gore dripping down his face. A tomb troll necromancer looks much healthier after consuming his gruesome feast!

I’ve never seen that before. And really don’t want to again.