Once the heroes have bested the climactic challenge at the heart of the dungeon, the story is effectively over. Requiring them to fight their way out is anticlimactic.

But it does seem like something should usually happen to them as they make their way to the exit. Perhaps one more combat? One last trap? These could be grid skill challenges (or just regular skill challenges).

1. Collapse! The place begins to collapse (due to the villain’s power dying, a self-destruct trap being triggered, the villain knocking over key columns, or divine retribution of the villain’s evil god), and the heroes must pass a skill challenge to escape.
2. Fire! The place catches on fire, and the heroes must pass a skill challenge to escape..
3. Guardians! Stone guardians are awakened to try to seal the party in with them.
4. Trapped! Disk-shaped stones concealed in the frame of doorways are released to roll into the doorways and possibly seal the party in, one random doorway at a time.
5. Crush! The ceiling of the final chamber begins to descend to crush everything flat.
6. Maze! The dungeon’s walls shift, turning it into a labyrinth.
7. Confusion! Censers light, releasing a hallucinogen that fills the dungeon, turning it into a confusing labyrinth. The heroes must make a wisdom check at each intersection or go the wrong way.
8. Poison! Censers light, releasing a poison that slowly fills the dungeon, lowest levels first, one level per minute. It first kills the minion that lights them.
9. Flood! Valves are opened that begin to flood the dungeon, lowest levels first, one room per minute.
10. Peril! The villain’s failed attempt to escape reveals an escape tunnel that presents one final peril: a river of lava! (…or grasping vines, deadly mold, an ooze, etc.).