The Master Engine is an object that appears in the Sonic the Hedgehog comic series and its spin-offs, and the Mega Man comic series, published by Archie Comics. It is a device that draws the power of merged worlds from the Unity Engines, and in turn feeds it into Sigma.
Sigma had Drs. Eggman and Wily build the Master Engine and the Unity Engines after taking over the Lost Hex, and contemplated the immense power he would gain through its use. His dream began to be realized when the pair of engines set up on Mega Man's World in the year 20XX and Sonic's World began feeding power to the Master Engine, which began feeding it into Sigma. Upon joining the force of heroes aboard the Sky Patrol, the two doctors revealed that Sigma's plan was to merge even more worlds together, granting him god-like power.