Not This. The. There is an entity called Q, but he's the one I've had the most dealing with. They're a collective of beings that live in a space between dimensions.

[He waves all around him.]

They can create realities all their own, and each one seems to have a personal sanctum. And perhaps most importantly, they have incredible, almost godlike power. They can bring people anywhere they want, they can grant abilities, and seem to have absolute control over real-space.