Here are some new/old modifiers that could be added, add your suggestions here too.
Randomized Alternate Floors: Removes alternate floor choice, you can’t pick the floor that is better for your load out and just breeze through it.
Afraid of the Dark: Makes the dungeon darker
Monster alert off: you no longer view the monsters yellow exclamation mark alerts when they see you, allows monsters to sneak up easier.
Double Bosses: instead of fighting - boss at a time per floor fight 2. This could be 2 of the same boss or 1 and 1 of different bosses (EX: King slime and crazed adventurer or double king slime)
Faulty marks: Marks with guaranteed perks now only occasionally work. (EX: Magicians mark only transforms relics 70% of time instead of 100% depending on difficulty)
Quiet dungeon: Monster noise level is reduced, allowing them to sneak up easier.