Board Thread:Theories and Rumors/@comment-30938718-20180317102920/@comment-32930549-20180510150952

The Overlord is the being that embodies the concept of Darkness and Evil in Ninjago. He started existing to counterbalance the Light and Good of the First Spinjitzu Master. That's kind of it.

So, saying that he is an evil counterpart of the FSM isn't too far of a stretch to say.