Bosses are the most powerful monsters in NeverGrind. Bosses have innate traits that make effects like fear and stun have a much shorter duration. They're also completely immune to some effects like charm. They drop anywhere from 3-6 items per kill. Revenant Viston has a -1 item drop penalty since his quest is so short. Bosses have the highest rare loot drop chance in the game. In particular, the first time you kill a boss on each difficulty there is a "first kill" loot bonus that sets the unique drop rates very high.
NeverGrind has the following bosses in the game: