The Autobot Matrix of Leadership (sometimes the Creation Matrix) is an artifact of great power, traditionally carried by the leader of the Autobots. By most accounts, it holds a part of the essence of Primus, the creator-god of the Transformers, although 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.
The Matrix and the concepts associated with it have continuously evolved over twenty-plus years, due to different Transformers fiction creating new ideas centred on it, which have in turn influenced its representation in other fiction, and so on, and so forth, and back-and-forth. The current nature of the Matrix as it is understood is beholden to quite a few different sources, and its development is described here to minimize confusion. For the specifics on the different interpretations of the Matrix in various continuities, see the "Fiction" section below.