From Teletraan I: The Transformers Wiki

The Mini-Con Matrix is a powerful object from the Armada portion of the Unicron Trilogy continuity family.

The Mini-Con Matrix was created by the Mini-Cons of Over-Run's universe who, unable to save themselves or their world from being destroyed by Unicron, merged their spark essences into an artifact which might give another universe hope for survival.

[edit] Fiction

[edit] Dreamwave comics continuity

The Matrix was brought into this universe by Over-Run, a Mini-Con who had escaped the destruction of his own universe. Over-Run protected the Matrix from Unicron's heralds, eventually bringing it under the protection of the Autobots. In a mission to rescue Optimus Prime, who had been shunted into Over-Run's doomed reality, Over-Run used the Matrix to enhance Optimus Prime and Jetfire's power to a level which might give Unicron pause. In the final battle with Unicron, the Mini-Con essences within the Matrix were amplified by the living essences of the Armada universe's Mini-Cons to help defeat the planet-eater.