When Barrowin of Clan Undurr enters, venture into the dungeon. (Enter the first room or advance to the next room.) Whenever Barrowin of Clan Undurr attacks, return up to one creature card with mana value 3 or less from your graveyard to the battlefield if you've completed a dungeon.
Barrowin of Clan Undurr (AFR-336) - Adventures in the Forgotten Realms: (Showcase)