The Black Dragons are one of the Loyalist Space Marine Chapters created during the Cursed 21st Founding; their gene-seed is suspected of having originated with the Salamanders. They were censured by the Inquisition due to the mutation of the Chapter's gene-seed, which causes certain Marines of the Chapter to develop blade-like outgrowths of bone on the head and forearms. Some Black Dragons afflicted in this way sharpened these bone growths and sheathed them in adamantium for use in close melee combat. These Black Dragons are then grouped together into specialist jump-pack-equipped Assault Marine squads known as Dragon Claws within the Chapter.
The Black Dragons are also known for growing very long, poison-tipped fangs. This level of mutation strains the tolerance of the Inquisition and there are many recorded instances of other Space Marines Chapters (notably the Dark Angels and Marines Malevolent) refusing to fight alongside the Black Dragons.