Matrix of Leadership

The Autobot Matrix of Leadership (sometimes the Creation Matrix or, rarely, the Autobot Matrix of Power or the Matrix of Light) is an artifact of great power, traditionally carried by the leader of the Autobots. Much about it, including its exact composition, remains a mystery. It generally appears as a hollow, spherical metal shell with two handles on either side and with a core sphere of blueish crystal at its center. The Matrix is the one thing, the only thing which Unicron fears.

MUX History
When Unicron arrived "early" on the MUX in 1997, Optimus Prime attempted to open the Matrix, but failed. Instead, Unicron was defeated by more conventional means.