Mantarin

Mantarin was built during the First Mendevian Crusade as a penal colony, but after Drezen fell, all contact with Mendev ceased. After realizing the gravity of their situation, the commanders offered all of the prisoners freedom as long as they swore oaths to join the crusade and fought against the demons of the Worldwound in an effort to make it back to Mendev. Unfotunately, the furthest any of them made it was halfway home, before the last of them were slain.

Today the penal colony is populated entirely by some half-fiends serving their demon masters. It's unknown what state the fortress and its population are in after the closing of the Worldwound.