the tainted dragon slayer (mira x oc)

What happens when even the grand magic council struggle to handle a problem? They turn to the strongest wizards guild in all fiore, Fairy tail.
in the guilds main hall everything is normal, natsu is fighting with gray, erza is eating her cake and the takeover bar maid mirajane is sitting behind the bar watching the fight while giggling when a messanger from the grand magic council enters the guild to speak with the master of the guild, Makarov. The messanger asks the master of he could send their strongest team to defeat an up and coming dark guild, "the river styx". Makarov quickly assembles the guilds prized team only to find that lucy is not present as she has fallen ill so the master decided the team could use some extra help but most of the other strong mages where out on jobs. When mir heard this she nominates herself to help out and the master agrees.
as the team gets ready to head out the messanger informs them that it won't be easy as they might have to face the dark guilds ace, pretty much the only reason they have been becoming more and more dangerous. Upon asking about this ace they get told something they didnt expect to hear. The council knew nothing about him other than he was known only as "the death bringer".
Around a month after the battle was fought, lucy felt much better and was heading back to the guild to find a job for her rent when she noticed a man around 21 sitting at the waters edge just staring into nothing. She checks to see if the man is ok and invites him to the guild so he can get something to eat and drink. Little did she know that things in the guild would get complicated soon after.
All Ch characters except oc belong to hiro mashima, the creator of fairy tail. the oc will be completely over powered and in the story there will be some other ships like nalu or jerza. it might get a little repetitive at times but as this is my first attempt at something like this plz dont be harsh and if anyone reads this id appreciate any feedback.