Thorn Cave

From Fiesta Wiki

Thorn Cave is the place where the boss, Karen lives. Karen spawns once a day, just like a regular boss. She will drop weapons and armor for around levels 99-110. To most,her level is unknown because her level is too high for the current level cap. There are lots of other high level mobs in thorn cave as well, protecting karen, most likely. They give great Exp alone, but they are hard to kill.