Ancalagon

It is unknown how Ancalagon actually looks like. The Dark Lords and the most powerful of their servitors appear significantly more aligned with the human minds - with, for example, Ancalagon and his servants appearing 'dragonic' - however it is not their ACTUAL look. It's just a self-censorship that human minds enforce upon themselves, seeing them as the closest approximation that they could handle. Ancalagon is established to have been capable of flight (although also in vacuum), and (due to the way his drakonic 'children' work like) have a tendency for ambition, greed or both.   Ancalagon's 'false look' made him appear like an impossibly large dragon, twelve thousand kilometers long (slightly above 1/4 of the Earth's equator). Both wings were of comparable size each. Reports on the colour, shape and 'texture' of his scales vary between every observer. Details vary on the colour (or even presence) of blood in the places where the scales were broken by the bombardment.

His wings were large enough to generate a deadly effect with every flap - people were crushed by air pressure, thrown back with deadly force, or had their flesh partially stripped from bones by the resulting winds (and that's without mentioning the flying trees, tanks, rocks, bodies, and dragon skeletons). All of that was merely a side effect of Ancalagon's movement - very few of those that happened to face his mouth survived to tell the tale, due to his breath attacks.   While details on those vary between the observes, each breath has thoroughly decimated hundreds of square miles of land. However, it is hard to say how exactly this attack worked - the same wasteland was seen as burned out, broken, drawn from life or frozen solid by different observers.

Next to nothing is known about his past. To Mankind, he is a member of the majority of the Dark Lord with no clues to their genesis. Perhaps he was always a Dark Lord - or perhaps he too, like Metatron, drove his people into extinction and ended up becoming a Dark Lord that way? With no evidence, you can make your own theories - just don't expect them to be backed up by something.   During the human invasion on Drakhrun he remained unnoticed for many months, despite the war ravaging the surface of his domain. Only when it become apparent that his servants are losing did he finally emerged - and did so literally. It turned out that his body remained underground, where it remained for so long that it has become part of the landscape. When he joined the fight, his body broke through the surface and showed itself to humans in its full glory, its length alone estimated at about twelve thousand kilometres.   The casualties sustained by Mankind in that battle were horrible. Ancalagon's scales resisted all but the most powerful of weaponry, with even the Universal Assault Units failing to cause anything more than surface wounds unless entire formations of those concentrated fire on a single scale. What saved human armies in that battle was mostly the fact that the Archdragon has barely woke up from his slumber - he was slow and his movements were uncoordinated (although his breath attack was still enough to flatten hundreds of square miles of ground).   With the wounds on its body amassing steadily, the Father of All Dragons made his last flight. Each of its wings clap caused air pressure that made servitors and human soldiers pop like balloons, while the winds generated by them peeled flesh from bones. His last flight was cut short when Mankind deployed most powerful of its weaponry, taking advantage of Ancalagon's retreat into space (and thus, lowered risk of the detonation decimating what was left of human armies in Drakhrun). In the end, his broken and inert body curled up, becoming one more of the many planetoids, giant asteroids and small planets scattered throughout the system.   Due to the Dominion's lack of interest in someone tinkering with the body, it is unknown which one of them used to be the Ancalagon. The issue become moot after the Blackout, which robbed Mankind of ability to visit other planets outside of Terra.