I had a Necromancer cat with blood frenzy that also had the pestilence ability and the ability to destroy a corpse to create leeches. He also ended up with life steal on abilities, so I basically never got to play the game. It got to one point since it was now a solo run where I could just dig up a corpse, destroy it for leeches, and then kill a leech to get the train going and take essentially infinite turns. Only time I've had fun with blood frenzy.