He was perpetually hungry, and a skilled soldier. The carrier of the knife (the disguised form of the Book of Dweia). Eliar could open the doors of the house that lead to anywhere or anywhen (in the books described as everywhen and everywhere by Gher) His task was to lead.
What I’m getting at is that everything is connected. Nothing happens in isolation. Eliar’s probably some crude, unschooled barbarian from the backcountry of Arum, but he did pick up the Knife back in Albron’s arms room. It might have been a whim, but we can’t be sure of that until we test him.