Krenaht:
We need your strength to subjugate the Giants.
I don't remember whether you have experience taking on Mimir. The frightening thing, though, is that Mimir has managed to resurrect not only himself but his minions as well.
First, in order to weaken Mimir, you'll have to slay the minions he has summoned.
The Mimillions, who are Mimir's minions, will appear when Mimir calls. When they do, take the opportunity to slay Mimir as well.
Slay the Mimillion Bathus, Mimillion Carcass, and Mimillion Kshana summoned by Mimir, then return.