In an interview with Forbes, World of Warcraft's lead narrative designer Steve Danuser elaborated a little on the role Wrathion will play in Dragonflight.
Heather Newman: Wrathion, the good son of a legendarily bad dragon, returns this expansion as a leading character. But he wasn’t shown in any of the preview footage of the expansion, unlike most of the other dragon characters. Has he changed?Steve Danuser: In terms of his appearance, Wrathion is going to maintain his handsome neer-do-well-ish kind of a guy who can make some questionable choices in the things that he's done over the years. He is really young in dragon terms and he has a very unusual origin. He was the fusion of dragon eggs mixed with outside influences. He consumed the heart of Lei Shen, which was brimming with Titan energy. So he has a very unusual origin story. And he's one of only a couple black dragons left on Azeroth that we know about him and Ebonhorn. So Wrathion's got a journey of his own. Unusual OriginSteven mentions that Wrathion is really young in dragon terms, but he's young in our terms as well. The result of a red dragon-led experiment to create a purified black dragon egg free of corruption, Wrathion first hatched during the events of Cataclysm. From the start, Wrathion made it clear he planned to be his own dragon — free not only of Deathwing's influence, but of the Red Dragonflight's influence as well. Wrathion says: No. I want him to deliver a message to the red dragonflight. Wrathion says: Tell them that I am free of my father's madness, and I will be free of them as well. I am to be left alone: this will be my first and only warning. Wrathion was also immediately ruthless, sending players on a series of quests to wipe out the
Read more on wowhead.com