This is to back up a bug report.

A fort was embarked that had HFS inside the lowest-level forges. The HFS was contained, hell was developed, eventually I tried "temporarily" retiring it to come in with an adventurer and equip him with adamantine. With demons all over the top level (not inside the fort much, oddly) he left via the underground roads, found a new fort, and was striking out.

But going 32 squares northwest, or travelling some distance and then hitting d, causes a crash. (You're OK to go south though. It might have to do with the *'s visible on the map northward)