Very brief and non fleshed out backstory for Celestine, going to expand upon later. Also if anything goes against the lore, let me know and I'll work something else out :)
Celestine was once a member of an incredibly powerful clan of dragons up in a far off kingdom. They were known for their immense pride, looking down upon all those they thought of as lesser. Celestine was practically considered royalty among them, the darling of his kin. He lead their soldiers, and was expected to one day become head of the clan itself.
Celestine was, however, overcome with hubris. His land had been plagued with wicked spirits for a millennia, sewing discord and fear. He believed that he would be the one to purify the kingdom. During his battle with the eldest spirit, he was gravely injured and struck from the sky. He was not killed though, for the spirit had other plans. As he fell, a terrible curse was placed upon him. His form changed to that of a human, albeit still with influences from his previous life. The spirit cushioned his fall with a pillow of wind as he descended into the ocean.
Celestine was picked up by a fishing crew, whom he threatened into bringing him back to shore. Dragging himself up to his Clan's layer, he begged for the mercy of his kin after his failure. The highest members of the Clan -- the people he had been raised by -- cast him back out, rejecting him for his failure and weaker body. Dejected and angry, Celestine declared that they would regret ever turning their backs on him. His passion fueled, he left hidden on the first merchant ship that arrived at the port.
He changed his name and identity, too ashamed for anyone to know what had befallen him. At the next port, he caught wind of a mysterious artifact that had the ability to reverse any curse and cure any ailment. Tracking down a ship heading to locate it, Celestine vowed his loyalty to the crew. To this day he is determined to break the curse, but what happens when he has to make a choice between his old family and his new one?