[Varyon]

A trap I made for That Other Game might work here - it had an obvious lock on the front and a hidden one in the back, which used the same key. Unlocking the front lock activated a trap the shot a poisoned dart and relocked the trap. It had 5 poisoned darts, and once the magazine was spent it would jam the lock from inside. Unlocking the hidden lock would disengage the trap, allowing it to be unlocked from the front normally. A proper rogue-type could figure out the mechanism and unlock it properly; a mage would likely get poisoned. My PC's never figured out the hidden mechanism and just bashed it open after 2 darts (ruining some of the potions in the process).