The Tree of Life

[Metathron]

Its quest instructs you to kill all the troops of orcs. I've pretty much cleared out all of the Great Forest area before I even got to the Tree, and after it I defeated a couple more armies that consisted of different kinds of orcs but also some other creatures like cyclops and bears, but it still says "Killed: 0/8"

So I'm wondering...which orc troops are meant here (somewhere else perhaps?)? Or is it some kind of glitch resulting from the fact that I killed most armies before I got to the Tree?