Oh I know. It's what's fun about this part. Each NPC has their own objectives, some stronger or more ruthless than others. Each has a differing level of familiarity and comfort with the generalized geography of the Underdark. Once you guys are out, and down a path free of Velkynvelve, Sarith can easily draw you a map of the area. Under duress, however, I'm wanting to see how much Bilda "remembers" of the Underdark's terrain to corroborate one stance or the other.