So a few things. 1: I was wondering if you could break 9999 in either mana or coin, you can. 2: If you have negative energy, anything that costs 0 energy cannot be used (was trying to use the gold whetstone using my energy restore items, yeah nope lmao). 3: I agree with a previous commenter that mage cap should probably only provide 3 mana per turn, since it's a single slot item that doesn't degrade other items when in the same row.
Rage ring might? need a limit per combat (though it does cost 2 per use. and in the first 9 floors it's acceptable. I'd assume anything that kinda breaks in endless is kinda okay, especially since floor 1-9 took me like 40 mins, but getting to this point took me around 4.5 hours, mostly to try for a 9999 mana cap.
Really fun game, might post some more random breaking the game stuff at some point. Would like to see a legendary wand/staff sometime soon, probably similar to the current staff cost wise (both energy and mana) to avoid, well... this lol. I'd say a high mana cost would work, but here I'm gaining 25 per turn (though I am on floor 21.)
I'll be checking this out daily, and always down to playtest and breaktest.