The Rouge Angel (Book 1) - HTTYD
He was Hiccup Horrendous Haddock the third.
During his time as a beat up, fifteen year old Viking, Hiccup started to change. Physically and mentally. He was getting powerful, violent urges, and his veins turned black, and started to show.
In the arena, when he was supposed to kill the Monstrous Nightmare, something within Hiccup snapped.
Something fell from the light...and something rose from the darkness...
Filled with this new power, and rage, Hiccup mounted Toothless, letting out the wrath of a Night Fury and his rider. Leaving the Vikings wounded, he flew off, away from Berk, and away from everything he had ever known.
Five years on, everyone thinks he's dead.
Until Berk meets the Rouge Angel...
((Warning; Contains some violence and gore))