Managed to knock out the Ultra Hard challenge today. Hit the wall in Depths my first handful of attempts thanks to the RNG gods not giving me much of a build to work with but took it down today predominantly thanks to Satanic Bible, Lost Contact, ???'s Only Friend, Thin Odd Mushroom, Jacob's Ladder and the Cancer trinket along with a clutch Cricket's Head in the Sheol super secret room. Having Percs pills on hand for the Satan and Mega Satan fights also helped. Ensured I had amazing tear rate that doubled as defensive shielding with lightning going off non-stop. Also had the Bookworm, Spun and Seraphim transformations in play. Even then it wasn't a cakewalk... was down to 3 1/2 hearts heading into the Dark Room.
I'm done with challenges now outside of the Glass Cannon challenge which remains inaccessible on Switch thanks to the Loki's Horns unlock glitch. I have at least been able to get the Horns added to my Itemdex thanks to Missing No. but that challenge won't be opening up without a patch.
After that fun, I now get to go back to the Greed mode well with Keeper. Yay?
Ultra Hard sucks. My biggest problem is you can't ever see the map and when combined with being teleported to other rooms thanks to curse of the maze it's just a massive exercise in frustration as you have literally no idea of your bearings at times.
I mitigated this issue by making use of
an online dungeon mapper tool. Made me feel like I was playing Etrian Odyssey again. Allowed me to do full floor clears and not lose track of anything outside of the unpleasantness of dealing with Curse of the Maze.