Humbold is the capital of Eru.
In the gamebooks[]
Humbold is never visited in the gamebooks, but it is mentioned in The Dungeons of Torgar. where Lone Wolf poses as an Eruan pathfinder. If Lone Wolf travels to Pirsi to meet Sebb Jarel, then he may meet a pathfinder captain in the town. The captain asks Lone Wolf where he trained as a pathfinder. "Humbold" is one of the three options provided. It is also an incorrect answer, implying that pathfinders are not trained here.