The Eternal Engine is central to the plot of SkyGunner. Somewhat of a MacGuffin, it is never explained how it works (though considering the limits of physics, this might be just as well) and it's never truly revealed. During the final battle, the player has to destroy a machine solider powered by the Eternal Engine. This solider is similar to those seen throughout the game, but vastly more powerful. It's unknown if the Eternal Engine is simply a limitless albeit conventional power source, or if it is something more fanciful and able to enhance otherwise ordinary objects.
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