Overview
A Hallowed Horn is a secondary quest in The Witcher 3: Wild Hunt, set on Ard Skellig in the Skellige Isles. It starts from the notice “Contract: Stolen Horn” on the board in Holmstein, or by stumbling on the bandit camp north of Arinbjorn where the horn is kept.
What happens
At the camp, Geralt kills the bandits and loots a chest containing the horn and a journal. If he found the camp first, the journal explains where the horn belongs.
In Holmstein, Mathios takes the horn back but is displeased that the thieves were killed. In his view, they were not evil men. He pays Geralt anyway.