Wolfskin is the first book of the Saga of the Light Isles series by New Zealand author Juliet Marillier.

[1][2][3] Eyvind is a young Viking man who wishes to be a Wolfskin (a berserker warrior of Thor) like his brother.

The Vikings quickly establish a peace treaty with the native island folk, and build a settlement.

Then Ulf is murdered sadistically, suspended by ropes from a cliff's edge to die of exposure, leaving his position to Somerled - who immediately breaks the treaty.

In the Viking hall, Eyvind's accusations are smothered with violence, and he is imprisoned, despite the efforts of his few remaining friends to help him.