When it comes to the One Piece world, fans know that Devil Fruit is the primary power system that Oda has introduced in his story. However, it is certainly not the only one. After or around the timeskip, Oda started to incorporate Haki more and more, and right now, this power system is very prevalent as well. It can be said that Haki is extremely important in the One Piece World, especially in the latter half of the Grand Line.