Generic high-fantasy setting (d&d 5e if you want to use specific spells), what security or defences would mages use to secure the place where they keep all their magical stuff? I’m thinking decoys, reinforced and hidden location, guards (hired or summoned), locks (both magical and mundane), booby traps, and spells to discourage or confuse passing snoopers.
Also it’s going to vary depending on the resources of the wizard and of the players. Is this an independent student wizard protecting their studies that a low-level party could reasonably break into, or is it the king’s secure vault of confiscated magical horrors that’s a final boss for the campaign?
I’m looking for ideas for fun obstacles, and critically that the players can’t just sidestep with a single low-level spell!
Three doors, each leads to 20 doors. The correct door leads to 20 more doors in the correct area, the rest will lead to 20 more doors each, all traps. Some rooms are insulting, with no trap and a single copper on the floor. One of those rooms will lead to 20 more doors, one of which is the correct door.