It's been a while since I played cleric, and I forgot just how strong they are. With Chalice of Blood and a Ring of Energy that I put all my SoUs into, I would have had to try to die. On the way back up, I Regened +7 hp per turn and one energy into the book every other turn. I could go into ascended form every time an enemy showed up if I wanted and would have full charge again almost by the time it wore off. No challenges since it was my first run with him in a long time, but that combo feels strong enough to carry in high challenge runs too, as long as you can make it far enough to get some upgrades into the energy ring.
Forgot to mention that I was running priest. Here's the score screen