I found something else about Ketheric in the Grove. It didn't register the first time I read that "historical scroll" because it only mention Ketheric and I read it long before getting the Dark Justicar story later in the EA.

The person writing the scroll blame himself for how Ketheric turned. Saying he didn't fall, but was pushed via causing him grief. And that shadow twisted his grief. The scroll is probably written by Haslin.