Oda is smoking some weeds writing this story. The defeated black Nika fell and create a hole, then it emerges as a black dragon with the Nika riding on it. So Oda indirectly telling us Loki is the black Nika. The black Nika who is imagined by the children to be evil and trying to kill them turns out to be their savior after it is defeated. It even give them the fairy tale amusement park ride with their parents. Peak fiction shit.