|Battle Cry||Fire and Bone|
|Successors of||Unknown (believed to be the Salamanders, possibly tyranids as well)|
|Homeworld||Gauntlet (semi-mythical, Chapter is officially Fleet-based)|
|Specialty||Assault, having pointy retractable arm-blades|
|Allegiance||Imperium of Man|
|Colours||Black with a white Aquila and markings|
The Black Dragons are a Space Marine Chapter in Warhammer 40,000. Part of the 21st or Cursed Founding, the Black Dragons suffer from mutation like the other Chapters of that founding. Specifically, they suffer from a mutated Ossmodula, which causes some gnarly bone growths to grow out of their forehead and forearms. It's unknown what mutation the Adeptus Mechanicus was trying to cure, as their Parent Chapter is unknown (they might've actually been trying to make them bigger and stronger- seems lots of Black Dragons are too large to fit regular Power Armour). Heavy speculation is that the Black Dragons are descended from the Salamanders, and those with more pronounced bone extensions are noted to have darker skin, reminiscent of the Salamanders' mutated melanchrome. The "osseovirus" responsible for the mutations was later isolated by the Haemonculus Coven known as the Hex and used to create the bone-mutating weapons known as the ossefactors.
Interestingly, rather than try to cure the bony crests, the Black Dragons instead embraced the mutation, having those with forearm blades coat said blades in adamantium and then inducted into special squads known as "Dragon Claws", and having them serve as Assault Marines (Space Marines + Wolverine/Baraka = awesome). They also incorporate this embracing of the mutation into their worship and doctrine as a chapter: such as the Chaplain calling upon the Emperor to "Curse thy servants" during prayer. This has raised more than a few eyebrows among the Inquisition, and several Chapters of Space Marines, such as the Dark Angels and the Marines Malevolent, have refused to fight alongside them (as if anyone wants the MMs anywhere near them, especially Salamanders descendants). Despite this, the Black Dragons are one of the few Chapters of the Cursed Founding still active as part of the Imperium of Man in late M41, where they committed nine of their ten companies to the 13th Black Crusade. They'd probably get on well with the Space Wolves.
They appear to have gained Primaris reinforcements with the dawn of the Dark Imperium, despite being a Cursed Founding (Or due to being so badass). The new KillTeam release mentions Black Dragon Reivers, and their prominent bone blades being used in KillTeams.
There is a novel featuring them, The Death of Antagonis. Quite a nice read, even while the description is misleading; the front and back covers feature Black Dragons fighting zombies, and while that does happen it's barely a third of the book. The last zombie "disappears" around page 90, and Exterminatus is declared 20 pages later; the next 200 pages take place on city world Aeghis Mortis and the main enemies are Tzeentchian marines lead by a Rogue Cardinal who is on a jolly trip to discover a world engine. One member of the chapter gets convinced by an Inquisitor to try and purge his mutated brothers, but when they both fall to Chaos he gets his ass killed for treachery and not embracing his brothers' mutations as a means to be even more effective killing machines. Not to mention the asshole Inquisitor got his stomach slit open by a pissed off Canoness.