"I was just taking a nap, and suddenly a young dragon ambushed me. Is that okay? It's not! I advise you, my dragon friend, to behave yourself and stop with this infighting. Don't try any more cheap tricks."
"Go die!" Twalin spat out a vortex of wind.
"You're not playing fair! No, you're not following dragon etiquette!"
I was just taking a nap in Mondstadt when I got ambushed, and then we started fighting. It went from a duel to a fight to the death.
A hundred years later, I, the evil dragon, crawled back from hell.
"Twalin, I'm back for revenge!"
"And you too, Barbatos, for interfering in a dragon's duel!"
PS: The protagonist is the evil dragon from the Stormterror cutscene. It revives after a long time has passed since its death.