It is a demonic dragon with sword horns, and it only serves those who bear the title of "Overlords". It shares the same ancestor with the hero "Dragonic Overlord". Hearing that its tribe bears the everlasting karma of serving the "Overlords" as their swords and shields, it was outraged for not knowing why the mighty demonic dragons have to serve a mere warrior, even if that warrior is a general. Its grievance triggered the worst result. Ignoring the warning from the old generals, it sneak attacked "Overlord" on the battlefield with those who agreed with its ambition. Of course, they failed to defeat "Overlord". This would have been a serious crime that could be sentenced to half-life imprisonment, but "Overlord" forgave it and left as if nothing happened.
There was an absolute difference of power between "Dragonic Burnout" and "Dragonic Overlord", and the difference could never be reduced. For this, the demonic dragon chose its master. Its meaning of existence is to become the sword of an absolutely mighty warrior, and it feels no grudge for this now.