All this talk about the Mask of Control and Makuta enslaving Okoto made me realize something.
And I'm going to go off the rails and speculate.
What if Makuta is not exactly Makuta? Umarak's bio mentions that he was born from the shadows. When he used the Mask of Ultimate Power, Makuta seemed possessed by something. Makuta was gone when he put on the mask, something took over him. So there's absolutely something else out there. Something far more terrible than Makuta lies there. Now, anyone else would say "Well, the Mask of Ultimate Power is alive and is controlling everything behind the scenes." But the Mask isn't alive. There's a difference between the Mask being alive and someone being trapped inside the mask. There's a reason that a Mask can't ever EVER have more than one elemental power. A sacred law. What if the reason for that is that there's something stuck inside the MoUP and Makuta freed that being when he made the Mask? Makuta is still unconscious. The TRUE Makuta. Ekimu's brother. What's left behind is a body possessed by whatever was stuck inside the mask, the "shadows." Controlling the Skull Creatures, giving Umarak orders, and he's in possession of the Mask of Ultimate Power.
TL;DR The Shadow was stuck inside the Mask of Ultimate Power, and Makuta inadvertently released it. The Shadow is the true antagonist of G2, Makuta is just a pawn, same as the Skull Creatures, the Beasts and Umarak.
Now to wait for someone to shoot this theory down easily by something I missed.