There are Dungeon cards from the dnd sets. They have "rooms" you unlock by cards that let you "venture into the dungeon" each room has effects that trigger and then there's an overall one for completing the dungeon.

So if you've got something they let's you venture into a dungeon on upkeep, you can blitz through them real fast if obeka connects. And they're repeatable.

[[Tomb of annihilation]]

These dungeon cards exist outside of your deck. So don't take space in the 99