Did Harald find out about Rox first then rip his horns out? If so Harald doing this makes a lot of sense. Dude just found out that his equal and his entire crew couldn’t stop the decimation of an island that was targeted and destroyed purely because one clan that lived there committed a crime in the ancient past.
No wonder he wants to atone for all giant transgressions in the past. As far as he knows, Elbaf could’ve been next.