User blog comment:Ash9876/Standard Magic and Lost Magic. Pros and Cons/@comment-30139950-20161217000221

Also! If you plan on writing a fanfiction set in the canon timeline, having a DS character would mess up the whole eclipse plot badly. The whole reason Cobra was released was so he could slay the seventh dragon, your character would instead be the one to kill the dragon.

Your oc can be badass and powerful without dragon slayer magic! Minerva and Kagura haven't got DS magic, yet they're extremely powerful.