Just wanted to put this random idea out there to see what people thought of it. I was thinking there could be a horn that would basically act like a weapon but the only "attack" it has is to blow the horn for a certain number of seconds( at least 5 seconds to deter from using it mid combat) alerting all nearby enemies of your location, and granting you and other vikings nearby a buff(Maybe +5 to all skills) for a certain duration. Obviously the numbers would need tuning/changing, but I think it would be sweet to have a "preparation buff" to use before big fights like a fuling village or something. There's a lot of potential for horns in this game, there could be one that pulses a knock back as you blow into it, one that does an AoE slow, or one that deafens enemies and forces them to temporarily scatter to make it easier to line of sight them and get that sweet sneak bonus again in a fight.
Let me know what you think!