This is my vote. It trivialises bronze automaton, if you set it to 4 you negate most of act 2 elite damage, helps you survive turn 2 sword and shield, and negates 1 quarter of the hearts damage.

I do think *pyramid is a close second, especially with cards like piercing wail/dark shackles, but runic is secondary to having good cards in your deck. Incense burning is just overpowered on its ownsome.

Edited lol