Can Boss Monster work with 5+ players?
I was just considering this a few days ago:

No, there are simply not enough hero types to go around.

Because the game operates on 4 basic hero types, it is limited to 4 players for fairness. (ie each player can concentrate on one hero type in a 4 player game: A goes Thieves, B goes Clerics, C goes Fighters, D goes Mages).

If you add more players ( E &amp; F ), then the players come into conflict over resource types ( E tries to go for Fighters. Suddenly, (depending on luck of the draw) either E or C is getting all the Fighter heroes and the other player gets nothing.

The problem magnifies more for each player as you add players beyond 4 in our thought experiment. Get to 8 players and 4 are unable to score any points.

Not very fun.

Edit/Update: Official Brotherwise opinion on the matter (from their website):


  Boss Monster 2 is balanced and recommended for 2-4 players. However, if you also own the core set, it is possible to play with 5-6 players. Here are some unofficial guidelines for larger games:
  
  Play using the Unlimited Lives variant described on page 17 of the rulebook. (Players are not eliminated upon reaching five Wounds. The game ends when a turn ends with no cards left in the Hero decks. The winner of the game is the player with the highest total Souls minus Wounds.)
  
  For a 5-player game, start with all the Heroes and Epic Heroes from one set. Then add an extra 4-Health Cleric, Fighter, Mage and Thief. Add an extra 11-Health Cleric, Fighter, Mage, and Thief.
  For a 6-player game, also add an extra 6-Health Cleric, Fighter, Mage and Thief.
  
  We are currently developing a set designed to facilitate larger multiplayer games. If you would like to share feedback on multiplayer over 4 players, please e-mail us at bossmonster@brotherwisegames.com!