Based on what i heard, Bosses appear in the 4th area (3rd sword) of the Campaign!!
Icerun Boss: Simbur
Goldsea Boss: Vespen
Darkspine Boss: Chiropta
Since you have an activity to defeat the bosses, im assuming that is Murkwood event related, in which both the Murkwood Consumed and Non-Consumed Keboko counts as defeating a boss! (<< The Enderlings don't count unfortunately, at least when i defeat them)
