At some point when the group is all together after Zyrithack has been enslaved in the black blade. The group is talking about what happened. Alexis speaks.

“Zyrithack mentioned Thun-Bül-Dor. Given the twisted path Zyrithack took to get to this location at this time, it could be anywhere. Given how close the legendary dwarven city of Dura-Intun was, maybe Thun-Bül-Dor is just as close. We know there are Dwarves under the Twins, and that the dwarves used to control the top of the Twins as well. There are Dwarves under Mount Sutheron, and perhaps they used to control its peak as well. Perhaps Mount Sutheron was Thun-Bül-Dor. Or the fabled Nadden-Tor. Maybe every major mountain used to hold a dwarven city. Maybe there are old dwarven cities abutting Middlebar fort. That could be a major boon for the rebels if that was true.” Alexis thinks on this for a moment.

“Maybe Mount Lanos has a dwarven city. Maybe Thun-Bül-Dor. Maybe Mount Kobos. Maybe even Nadden-Tor!” Alexis gets a far-off look and a smile starts creeping up his face. “Or… Mount Avernus…!” Alexis looks more serious “No. That doesn’t seem right.”

“I need to get a map of all the major mountains. They could all have dwarven cities!”