The Hunting laws give the following definitions of boss:
- In Mythic Nexus caves boss is defined as a foe that drops a key and/or other special item and/or money and spawns in certain rooms. The boss will differ in appearance from other creatures in the cave and give more experience.
- Outside Mythic Nexus caves boss is defined as a foe that differs in appearance from other creatures in the cave, drops a rare item, and makes seldom appearances inside the cave.
In terms of source code script, a boss is a class of enemy that nearly always spawns inside a dungeon. Enemies with the boss flag ID are usually the strongest enemy inside the dungeon.