The Umbral Halls is a dungeon located at 75.8s, 83.1e near the town of Kryst on the Vessayan Islands. Inside can be found a variety of Shadows, Mosswarts, and their Idols.
It is also part of the Bleearg's Gratitude quest.
Most visitors to the dungeon, however, are interested in the wide variety of portal destinatins that can be found inside.
There are four branches in the dungeon, each with 5 portals. The branches are:
North Branch
West Branch
South Branch
East Branch