The Fallen Magician was reborn as a Dragon

The strongest Magician, Ethan, was bored since he was unmatched among his humans peers, then, he challenged the Dragon King, after fighting for 1 week in a roll, both him and the Dragon King perished. He thought it was the end of his boring life, but he suddenly open his eyes again and as he inspected his body, he was a.... Snake? Fate surely love to do jokes. OBS: I found the cover in the google, i do not own it.