The Dwell of Souls is a location on Eternia and appears in the Turtles of Grayskull (mini-comics). To reach the Dwell of Souls, one must travel beneath Castle Grayskull.
In The Spirit of Gray-Shell, Sorceress sends the Turtles, April O'Neil, and Casey Jones deep into the bowels of Castle Grayskull to seek out the Dwell of Souls. It is a spacious, dungeon-like room, with prison cells containing all manner of odd creature. The prison cells are fortified by magic, because many of the creatures contained within are extremely dangerous. At the center of the Dwell of Souls is a circular pit in which a blue fire burns. The pit allows April, who has been given sorceress powers, to activate them. It is in the Dwell of Souls that Splinter, infused with the Spirit of Grayskull, appears to them. He tells the Turtles that the Power Sword calls through him. With this communication comes its location on the Forgotten Island.