Cultist's Horn

The horn is only obtainable by looting a Cultist. It's partially a quest item and you need to equip the horn and blow it (sounds like a big boat) in order to summon the Cultist Elder.

Effects
Currently the only effect the horn does besides being handheld (visible), is making a loud and heavy sound, which is used at night to summon the Cultist Elder. Whether or not this is it's only function is not yet known.

Trivia

 * The Cultist's Horn is mountable on any mounting plate.

Source

 * Helping The Innkeeper (quest)
 * Cultists