Get ready to turn one of the best rogue-like's into one of the best co-op games! Together In Spire is a comprehensive mod that re-imagines the game as a full multiplayer experience for up to 5 players.
The gameplay doesn't change a huge amount from the single-player experience other than now needing to work together as a team to take down the hardest baddies together.
All (up to 5 players) play their turn (one at a time or all players at the same time). When the turn ends, the (now harder) enemies attack all players. Players don't need to follow the same path together, but for success, it's highly advised.
First, you'll need to "subscribe" to the mod on the Steam Workshop page:
Steam Workshop::Multiplayer Mod - Together In Spire - ALPHA
Make sure that not only the Together in Spire is subscribed, but the 3 dependencies are also subscribed.