[Flere821]

Originally Posted by Wilfriback

Can anyone tell me about Brimir's main objetive to the point of commiting large scale genocides and why or how Sasha did to kill him?
The guy wanted to fight an enemy which was the ultimate treat to any living being but it wasn't unveiled, I think.

Spoiler for answer:

Brimir killed the Daliaku/Valiag because he had no choice - He basically had two choices, either commit genocide or have humans wiped out from the continent. He chose the genocide option.

Sasha killed Brimir by stabbing him through the heart with Derflinger, after for some reason he tried to genocide the elves as well. Reasons not yet shown in LNs.