Vildkaarl

Vildkaarls (meaning "wild men" in Skellige jargon) are a brotherhood of warriors in Ard Skellig highlands, independent of any clan. They eat what they hunt and live only to kill.

What's unknown to rest of the islanders is that they secretly worship the forbidden deity Svalblod and all the blood they spill is meant to be in sacrifice to him. The remaining priests of Svalblod submit vildkaarls to trails meant to ensure only the strongest individuals pass and then recreate them into werebears ("berserkers" on Skellige) via ancient ritual.

History
In Skellige's formative years, when acolytes of Svalblod nearly drowned the Isles in blood, a short civil war erupted between the cultists and the rest. During it, berserkers committed mass murders and massacres until they were defeated. Worshipping Svalblod was then forbidden, his priests and followers bound on ships without sails and cast out to sea, henges brought down.

However, one small henge in Fornhala, the once-lively seat of Svalblod's cult full of ancient temples dedicated to him that had fallen into disrepair, survived. Fornhala's secret underground caves were where a few priests hid and began creating vildkaarls.