(First floor.) Ration of Food blocks the door. Mage pretty much starts with everything you need to solve that room.
Edit: This seed is crazy, already with artifact and wand on the first three floors. LBX-MZH-SYDv2.5.2 (Mage; On Diet&Faith Is My Armor&Forbidden Runes)
No, I can go on exploring the floor and then go to that room when I’m back at the entrance … or go there when I’m out of staff charges.
edit: No, I’m wrong. It only feels like taking longer, but the detour would take more turns. Unless I have to wait for my staff to recharge anyways.