Deeplough was a large crater on Green Isle filled with water of immeasurable depth. It was home to the Slothunog. It was known as an evil place to the otters of Green Isle, as Riggu Felis would throw miscreant slaves into it to be eaten by Slothunog. The route to the otter holt, Summerdell, passed along the rim of Deeplough. Pitru set up his rebel base on its rim, which was then attacked by the Long Patrol, Lady Tiria Wildlough, and the otterclans in the Battle on Deeplough's Rim.
Deeplough appears in High Rhulain.