I see, thanks for answering. I think I actually got that horn in Plains of Leranse the first time I killed the hexer, but then I reloaded the game so I could reach the gold victory and after that I couldn't get the item no matter how many times I reloaded or killed him with different units.
The quest in Wings of Verson I'm not very sure about, I "may" have killed him with a level 5 unit and "maybe" he already had the fear perk. I'm certain I never got the horn in Plains of Leranse though.
Doesn't really matter now as I've completed the human campaign already but it was bugging me at the time
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