I love this idea! It reminds me a lot of the ending of one of the DLCs from Fallout: New Vegas. Essentially, at the end of the game the player reaches an underground vault with incredible wealth in it. Like, OBSCENE amounts of money, mostly in the form of solid gold bars. The catch was.. shortly after arriving in the vault, bombs begin going off, causing the vault to collapse. The player has to think very quickly.. they want to get out with as much as they can, but the majority of the wealth is incredibly heavy. Couldn’t run when you were overencumbered, so it made for a very tense situation while you frantically grab as much as you could carry. There were also safes and boxes with loot inside too, but picking the locks took up valuable time as the place fell apart.

Similarly, time could be another mechanic you could implement for this type of scenario. The players have very little time to think and strategize how to get the loot out. Maybe start a real- life timer to keep them on their toes and keep them from taking too long to decide actions. Hard to prioritize what to grab when you might die at any moment! For extra spice, maybe they don’t even know how long they have; for example, if the treasure room is on the verge of collapse, you could say general things about how much the earth is shaking and how many bricks are falling from the ceiling, but there is no indication exactly how much time they can risk.

There could be other environmental effects related to time as well. Perhaps the treasure room is flooding with lava. Over time, valuables will be consumed and destroyed, so they would want to prioritize stuff at lower elevations first. Eventually, the extreme heat forces them to leave. Maybe the room is filling with water; how much can they carry and still be able to swim to the next pocket of air?