The Black Cube of Darkness is a seemingly ominous object who was considered to be concentrated evil and only speaks in Latin with a deep demonic voice. He was formerly one of the most powerful and evil villains in the galaxy and had dozens of planets under his control, but eventually gave up villainy after failing to acquire the "Ring of Invincibility" in a humiliating event. He has since reformed with the aid of Wander and found a new lease on life.
The Black Cube was a being of pure evil who terrified and stole the souls of those around him and spreading his influence throughout the galaxy. He wouldn't hesitate to become even more powerful if given the chance. Despite this and the fact that he is pure condensed evil in a cube, the Black Cube of Darkness is actually quite self-conscious about being a cube and becomes incredibly saddened when realizing that he has no limbs or a proper living body like other beings in the galaxy. Eventually this self-conscious attitude led to severe depression, which showed that that the Black Cube was actually a sensitive being who wasn't purely evil.
The Black Cube is a powerful being who can destroy his enemies on a deeper level than physical. He can steal people's souls simply by speaking to them. The only way to avoid having one's soul sucked is to completely avoid eye contact with the Black Cube. Victims of the Black Cube's power are rendered unconscious after looking at him and their eyes will become pitch black as their souls are stolen, however the Black Cube has the ability to return them as well, but his victims seem to be slightly drained and confused afterwards. The Black Cube can only steal a soul if he stares at a victim for a prolonged period, making his powers truly dark and terrifying and alsho has telekinetic powers which he once used to crush a cash register, but he might only be able to use them when truly angry, as he doesn't use this power to touch or move things, instead moving or pushing them with his own body most of the time as though he had hands, which he doesn't. His body is also seemingly indestructible as shown in "The Battle Royale", where General McGuffin's missile was rendered bent and useless after coming in contact with the Black Cube. In "The Battle Royale", its power to steal souls was on par with Little Bits' power to control them and both were seemingly immune to each other's influence.
In the Fancy Party celebrated by Queen Entozoa, the Black Cube was one of the many villains who attended her fancy dinner party in hopes of inheriting her army and power. During the party he attempted to intimidate Lord Hater and Commander Peepers while in the bathroom. Later Sylvia pushed Peepers onto the Black Cube, causing the Black Cube to steal Peepers' soul.
Later, in the Battle Royale, the Black Cube is shown battling Little Bits for the ring of invincibility, and later on, it reaches the ring, but fails to obtain it due to it lacking any hands. Its fellow villains look on with shame, disappointment and laughter which causes the Black Cube to sadly float away as he realizes his limitations.More later, in "The Black Cube", after suffering his most shameful loss when he failed to obtain the Ring of Invincibility, the Black Cube could no longer go on as a villain and quit.