Well, Fields of the Dead (FotD) is a bit to the northwest. The Chionthar is where all the mid-land cities are and trade routes pretty much go around the FotD.
I noticed in current playthrough that the mountain pass route has a sign saying 'Closed due to inclement weather', with Flaming Fist nearby to enforce it. Seems like Baldur's Gate has been putting serious effort into keeping Moonrise's death curse a well kept secret.
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I get a major Skull Knight vibe (Berserk manga) from the undead oath-breaker guardian. If he's anything like that character, he's hanging around for his own agenda, not for any great love of the MC.