load bearing monster
A fantasy/sci-fi cliche, wherein the defeat of a given villain triggers the catastrophic destruction of its immediate environment, ie: the dungeon collapses, the planet explodes, the spacecraft implodes into the 37th dimension, etc.
Game Master: "The giant falls dead, but just as you think you're safe you feel the floor of the cavern begin to shake and rumble ominously."
Player: "Aw crap, he's a load bearing monster! Loot the body and run!"
Player: "Aw crap, he's a load bearing monster! Loot the body and run!"