The Control Cube is a small cube-shaped artifact that appears both in Might and Magic VI: The Mandate of Heaven and in Might and Magic VII: For Blood and Honor. It is a very important quest item in both games, and also, very late in both games.
The Control Cube was created by the Ancients before the time of Silence, and first appeared on the continent of Varn, where it was carried as a symbol of might. It is heavily imbued with magic, and it has a strange purple glow. As the ruler of Varn was defeated, the invaders took the Control Cube. Although the invaders of Varn were defeated shortly thereafter, the Cube was retrieved by the people of Varn, and it was transported to safety, being placed in a heavily fortified place, surrounded by ageless guardians immortal to time, and forgotten for a long time.
Hidden in Enroth
The Oracle of Enroth, an omniscient source of knowledge being able to look into the future, spoke to four heroes of the land after they tried to solve the mystery of the devil invasion, followed by the Night of Shooting Stars. The four heroes of the land, after gaining access to the Oracle by solving major quests for the lords of Enroth, was told that the ancient Tomb of VARN, far away in the deep sands of Dragonsand was the place to look. The four heroes entered the pyramid and fought themselves through the major defenses the Varn people had set up - in addition to hundreds of guardians and sentinels, a strange radiation inflicted pain upon them as well. Eventually, they fought themselves into the heart of the pyramid, unlocking the Well of VARN. There it was - the Control Cube of Varn. It was brought back to the Oracle of Enroth, and used to enter the Command Center. Ironically, the center itself contained several more control cubes, but one was necessary to enter it in the first place, and there seemed to be no other use for the cubes on the continent of Enroth.
Reappearance in Antagarich
Eight control cubes were brought to the world of Enroth after the adventurers of Terra landed on the planet. As later they split into two separate factions, each allied to opposite and antagonistic factions, both Bracada and Deyja possessed four Control Cubes. In the events of Might and Magic VII the party of adventurers is required to retrieve another Control Cube for their alignment, so that they can possess the majority of them for an undisclosed reason (presumably required to enter the Lincoln).