Eikthyr event - Boars and Necks attack - Locked out after killing Eikthyr
Elder event - Greydwarfs/Brutes/Shamans attack - Unlocked after killing Eikthyr Locked out after killing The Elder
Bonemass event - Draugars and Skeletons attack - Unlocked after killing the Elder Locked out after killing Bonemass
Moder event - Drakes attack - Unlocked after killing Bonemass Locked out after killing Moder
Yagluth event - goblins attack - Unlocked after killing Moder Locked out after killing Yagulth (unfortunately this one never triggered for us before beating Yagluth)

Variety is nice, and the other events also provide other desired materials. Resin is always welcome, meat, intestines, freezing glands.