idk where you'd put it but I want some insight upgrades just for arena. Because most of these aren't exactly the most helpful, they can be individually disabled and enabled to spice up gameplay.
some examples:
A Third Option: an additional relic/curse choice is presented when waves are completed.
Layered Treasures: more treasure rooms are located inside the two locked treasure rooms.
Gifts of the Arena: sometimes platforms can produce gifts for you like pots and chests... or less favorable things.
Eternal Unrest: The arena will now shift WHILE you're fighting, producing a more dynamic environment.
Uncovered Taboos: Expands the amount of curses... but don't worry! Some aren't as bad as you think.
I would add more but I kinda ran out of ideas lol