The party of adventurers is questing for a magical sword, and seem to have found it in a treasure room deep in a dungeon. The room is full of gold, trinkets, whosits and whatsits galore. On a pedestal in the middle of the room is the sword!
As soon as the players grab it, all of the treasures (including the sword the players have been questing after for weeks) crumble to ash, the door they came in slams shut, and molten lava starts slowly pouring into the room from every corner. They have to think fast about how to get out!