Greymaul Rebellion

Among the stories of the Longbeards is that of the Greymaul Rebellion. In the First Age, Durin the Deathless left his halls to seek a safer home for his people than Gundabad, which was under continual threat from the servants of Morgoth. Durin would find what he sought far to the south, in what became Khazad-dûm. In his absence, he named Mótsog, his closest friend and a great warrior, Lord of Gundabad. Mótsog then led a revolt against Durin as leader of the Greymauls, building his own stronghold in Sundergrót. The Greymauls ruled Durin's holdings until Durin returned and put Mótsog to death in a battle in the heights of High Sundergrót.

The story now is a cautionary tale among the Longbeards, a warning that even one's closest friends might be tempted to treachery. A mosaic of the death of Mótsog can be found in Nabgûn-mazaru, in Erebor. ^{[14.0N, 136.3W]}