There are two types of bosses: Bosses and Mini-bosses. Bosses are only encountered in missions that require you to slay the boss. Mini-Bosses are encountered roaming in the hallways of any mission. There are only two Mini-Bosses in the base game (the Shambler and Collector) with two others being added with each DLC: Crimson Court DLC introduced the Fanatic and Color of Madness DLC the Thing From The Stars.
Unlocking bosses requires successful expeditions in the relevant location. The longer the expedition, the more progress is made towards unlocking the boss.
In detail:
For Apprentice bosses, successful short expeditions will increase the unlocking progress by 50%, medium by 75%, long by 100%.
For Veteran bosses, successful short expeditions will increase the unlocking progress by 33%, medium by 50%, long by 67%.
For Champion bosses, successful short expeditions will increase the unlocking progress by 25%, medium by 30%, long by *40%. *(source: ingame observation from July 8th, 2018, Bloodmoon difficulty).
Excess unlock progression from expeditions which unlock the boss DO appear to carry over to the next boss. (egs. at 50% progression to unlock apprentice Hag, a medium mission will unlock the boss AND progress to unlocking the apprentice Brigand Pounder by 25%)
Tips[ | ]
When locating a boss, it is almost always the room farthest away from the entrance room. If two rooms are the same length away, it's the room furthest down. If both rooms are on the same height, it's the one further on the right.
Corridor length does not affect "how far away" a room is, only a count of rooms themselves between your room and the boss room.
Try to trigger the event that gives 15% damage before going on a boss quest. It can help you finish the quest more easily. Read the Town Events section for more information.
Finding Mini-Bosses[ | ]
The Shambler and The Collector are bosses that can be found on any mission in the base game; however, they can only be found under certain circumstances;
The Shambler can be found in 2 ways; either in a hallway encounter if the light is at 0, or if a torch is used on a Shambler's Altar.
The Collector can only be found during a hallway encounter if the player's inventory is at least 13 slots full.
For the Fanatic if you have 2 or 3 heroes infected, the chance of him appearing are 20% and 33% at medium and high infestation, respectively. If all four of your heroes are infected, there is a 75% chance at both medium and high infestation. A special loading screen will warn you that the Fanatic is in the dungeon.
The Thing from the Stars has 50% chance to appear in a hallway in a designated area, which is marked on the map screen prior to selecting a mission with a special icon.
This article or section may contain spoilers about the final boss. You might want to avoid reading further if you don't want to spoil the surprise for yourself!