The weapons sister (luffy x oc)

Legend has it that the ancient weapon of the merfolk, has a protector. Most would say that the sea kings are her protectors, but no...

Even the sea kings, dare not go face to face agents this protector, for the last that has, was dragged to the depths of the ocean, never to be heard from again.

So what will luffy and his crew do, when they come face to face with This guardian, Who was said to protect the northern seas so Fiercely, that not even the strongest of Pirates go near those waters.

(I DO NOT ONE PIECE OR ANY OF THE CHARACTERS !!!)