A new Assassin's Creed Valhalla patch 1.1.1 update has fixed a ton of quest bugs that've plagued the game since its November launch. The game released with a ton of mission bugs that simply prevented players from moving forward, including a multitude of side missions....
I suspect that it would be something like a specialized horn of valhalla. Well, even then, we're dealing with a very powerful magic item. I just hope they commission a non-horn-y (<- haha!) version of his art to grace the PFS pregen printouts that they HOPEFULLY will have of him...