Steam Cave is a dungeon in Pokemon Mystery Dungeon Explorers of Time, Darkness and Sky. It is the last dungeon in the expedition. After activating the Groudon statue to clear up Foggy Forest, this dungeon will be unlocked. The first time around, Groudon appears as a boss. This proves to be an illusion made by Uxie to guard the cave. After rolling the credits, Uxie will be waiting as a boss here.
Turtwig, Piplup, Glameow, and Aron exploring Steam Cave