Duke Pantarei, the Hero of the Great War.

His goal was to save the world, but perhaps his method was the wrong one.
He had been willing to sacrifice humanity for the sake of the planet, but in the end his strength wasn't enough.

So he gave the humans one final chance, but something strange happened in the process.
This place...it can't be Terca Lumireis...can it?

Tales of Vesperia crossover.
No knowledge of the game is really needed, but it would help if you at least read Duke's wiki profile or something.