Fairy Tail's Doomslayer

Demon's, after the battle with Zeref and Acnologia a dark guild wanted to take over the Kingdom of Fiore, they used a forbidden spell that opened a portol to hell, but when they did Demon's came flooding in killing and destroying everything in sight, as everyone built walls around the city's and tried living a normal life, but one day all Dragon and God Slayers had the same dream, they dreamed of a being that stronger than any dragon or God, this being was the Doom Slayer, a Demon's worst nightmare