Well i don’t think they have ever been on the same side exactly, but they aren’t really ultimate enemies either, in my opinion. It is like if you think of it the other way. In one way you have Rumpel’s side with him doing what he is doing working with people and then Regina is on another side with all of her minions doing what she is doing, but if you look at it the other way it is there are people who have power and people who don’t. So in that way they are both people of power and on the same side because they desire to keep their power and so in some way they work together because it makes them both powerful to do so even though in the other way they are different sides. Does that make sense?
It is just in one way they are working together and in another way they are not. And i just can’t imagine that Rumpel’s end game is really just to defeat Regina. There has to be more to it then that i think. Maybe Regina has part of his power somehow. That when whatever happened between Cora and Rumpel back in the she’s just a miller’s daughter days she was able to get a bit of the dark one power and then when Regina killed her mother that power was passed on.
I don’t know. That was a lot of speculation. I just don’t see them as the ultimate powers here. Rumpel has been around for centuries, but Regina seems to be just a regular person who went evil. Maybe it is just i think that the good should be a side instead of just evil vs evil.