The Pictish king Bran Mak Morn visited the moor himself to get his revenge on a Roman commander. The king explored the moor seeking a "door" to the world of the worms of the earth, who he wished to use against his Roman foes. He also visited a deep pool where he stirred up Dagon, and a set of standing stones.
It is unknown whether the moor still exists or has the same name in the modern day.
Dagon-Moor is in the west of the British Isles, near Wales. The moor contains several oddities. These include a large and possibly bottomless pool, where an "unspeakable creature" lives, probably Dagon. Similarly a circle of standing stones also is said to be connected with Dagon.
The moor also contains the lair of the worms of the earth, a degenerate tribe of reptilian human castoffs. In a burial mound in the moor is a a secret entrance to a worm temple. There on an altar of human skulls is the Black Stone. Another tunnel is secretly gained from a cave. Stairs descend far into the earth to where the worms live. It is highly likely that many more tunnels exist, as the worms have learnt to burrow through the earth like their namesakes.