Eld, the Living Volcano

Eld is a red dragon who allied with four other dragons, fighting in the dance of dragons to attain more might than many other mortal beings ever possessed. He spent much time in the plane of fire, researching how he can enhance himself or maybe even parent a new kind of dragon. Eventually he managed to transform himself into a magma dragon. There is nothing know about his whereabouts but rumors tell he was slain, although his remains have never been found.
Eld was known as highly intelligent and ambitious, not caring about morality, empathy. For Eld, rationality was clearly superior to emotions, altruism especially being completely alien to his selfish, utilitarian mind.
Referenced in this oneshot Born in Magma