The Cosmic Cube was introduced in Captain America storyline called Tales of Suspense. It was created by Advanced Ideas Mechanics and is used to alter reality itself. Captain America villain Red Skull has an obsession with the Cosmic Cube, after it was taken away from him by the Captain. Over the years, he has either tried to take it back or tried to recreate a new one. The Cosmic Cube has been revealed over time to be eggs of cosmic beings.
White Lantern Ring:
The White Lantern Ring has all the powers of the other Lantern rings which would make it one of the most powerful weapons in the universe. It can control the Life Equation which makes it contain the power of life itself. The ring’s power was too high, so Kyle Rayner[the only being to have been the bearer of the White Lantern] split the ring into seven rings, with each ring bearer controlling a piece of the powerful Life Equation.