User blog comment:OverlordRocks/The Ethereal Divide in S7?/@comment-27507964-20160502033742

The weapons could be what is tying the villains back to their original times. It is a piece of the ninja's past, the villain's present, which is a key part of them.

And I explained why Yang doesn't like the ninja. He requires Cole joins his other students and the ninja oppose him, as any friends would. To get to Cole, Yang has to go through the ninja, and he needs help with that.