Lord Xy
A mysterious, amnesiac human released by the Heroes from suspended animation in an old dragon temple infested by kobolds. 7 foot tall, heavily muscled, and square-jawed, with wild, wavy, fire-red hair and penetrating blue eyes, he disappeared soon after, only to reappear a year later in Telleconia, calling himself "Lord Xy" and leading the Dragon Pride cult, becoming a foe of the party, despite feeling somewhat indebted to them still.
More than a year later, the party returned to Telleconia to find Xy, Dragon Pride, and many chromatic dragons in full control of Telleconia and its environs. Since then he's been trying through minions to capture or kill the party.
Xy was eventually revealed to be the human form of the ancient red dragon of legend known as Xygarius the World Breaker, who seeks to destroy Alech'nor until it forces the ancient gold dragon Mallixitofaxus, ruler of the Council of Dragons, to speak to him.
Eventually Xygarius and his army of dragons from all over the spheres conquered Alech'nor. The Heroes collected the Dragon Orbs to defeat him, along with find that the Dragon Council had been driven from the High Throne by armies of void dragons. The conflict finally came to a head over the city state of Isulla in late Fifthmonth of 7169, after many of Xygarius's dragons had rebelled against him and warred against each other. The Heroes fought Xygarius and two female adult red dragons. The younger dragons were slain, as was Falben himself, and The Autumn Moon was destroyed by Xygarius.
Cura and Kaneatsu fought him in the air, however, and Mix, summoning the last of her strength, fired three massive lightning bolts into the Great Wyrm, who seemed to have stopped defending himself. He seemed to die, before all faded to white light and the dead or dying heroes were restored.
Then Mallixitofaxus appeared with the still barely lived. She explained that all dragons were ascending to a higher reality, and then they did. Dragons are no more, throughout the material plane.