Woah woah woah-- What?! I'm pretty behind on Ben 10 (especially any info that came from the second reboot, the one where bens 14-15) BUT EON IS BEN?! Honey, you ain't looking so swell in your older years... Is there an episode I can watch where this info is given???
Okay I have this weird theory. What if that Ben came from a world who had an Omnitix, but had it taken away? The armor that Eon wears is some ancient alien artifact that when Ben put it on the temporal energies rapidly aged his body and gave him complete insight into other realities. It drove him mad and it helped to fuel his lust to destroy Ben Tennyson and even enslave many of the Bens from the multiverse.