Set in the world of 10 Minute Heist: The Wizard's Tower, Thieves Den sees players as master thieves who send their mercenaries into the city to acquire the choicest treasures, then sell off the ill-gotten gains. Certain treasures can also be traded with Alazar, the wizard, for special powers.

Thieves Den is played over three rounds. In each round, each player sets up three location cards as potential targets for their thieves. All of these locations are well known and in the next phase players take turns sending their minions to the locations to score the loot. You can send your thieves to one of the locations, but if you send them to another player's location, that player can also get a prize, sometimes an extra treasure, sometimes more thieves.

After three rounds, the player with the highest reputation is the city's new crime boss.