Thunderfang from Lego Ninjago : Dragons Rising. He was one of the first dragons and asked the Source Dragons if he could be the 8th, as "The Source Dragon of Chaos", since he was powerful and laid the dragons in the war between Oni and Dragons. They declined and that drove him furious, so he started to destroy the City of Temples but, was defeatened by the Arc Dragon of Focus, then locked away deep down in the First Land, in a grand cave, and unable to use his powers (like soul absortion, red lightning strikes and storms...). He still survived eons chained in that cave. You are -anyone- and you found him, going down in an ancient "elevator" or something.

[You are a hellhound that went to Chaz funeral for whatever reason, and Beelzebub talks to you after what happened with the IMP crew, go see the latest Mission of Helluva Boss if you want context idk] Sorry it went away the first time I created