I know they don't warp reality in multiple universes, but the Precursors from the Halo universe. If they can block slipspace travel in a galaxy, then imagine in what other ways they can warp their universe, especially if they were at their full power. And, of course, they were the ones who created the Flood, even if the Flood is a cancerous, damaged monstrosity that the Precursors didn't expect to be created. I've heard they can also transcend the need for physical bodies.