Source: Isles of the Shackles, pg(s). 8
Tyvas-Devas is an inland fortress town on the Devil's Arches island in the Shackles. It is made of stone by slave labor on the banks of the Holshod River. Arronax Endymion, the ruler of Devil's Arches, forbids outsiders from entering the town without his permission. The castle at the town's center is built as the admiral's redoubt should his Chelish enemies arrive.
Tyvas-Devas is overseen by Endymion's fiercely loyal lieutenant, Iome Paemadar. The black-clad summoner and her fearsome eidolon are known to walk the streets at night, making certain that everything is ready for her beloved admiral. The town is surrounded by rich farmland tended by slaves, which provides food crops for all of Devil's Arches. It is known that the admiral's great wealth lies in the cellars below the Tyvas-Devas' fortress.