The Cosmic Cube is an item that can control matter and energy, answering to the will of the sentient beings that use them. They require practice to be used properly, but a skillful user can alter all reality to answer to its thoughts, granting anything they desire. Thanos held the Cosmic Cube in Captain Marvel #28.
For any fan of the Mad Titan, this Thanos Cosmic Cube Marvel Comics T-Shirt is a must have!
