Hello, Shiv here! Please excuse any grammar mistakes, 8th grade is hard. I have a theory for you guys to ponder: Mecha-Jaraxxus isn't the real one who created the Rusted Legion. He is more like a pawn. But, if he isn't commanding the risen demons and heroes, who is? Someone we already met: Mecha'thun. There is evidence that links this mechanical entity to the Rusted Legion.

First of all, his quest to end fleshings. He states in his entry quote that "The era of flesh has ended."  The Rusted Legion is an army of reborn heroes and demons with mechanical upgrades.It seems plausible for Mecha'thun to meet up with Mecha-Jaraxxus and convince him that they both have a common goal: destruction of flesh and blood. Or he could be still locked up in Boom Labs and whisper in his ear to do that instead. 

Another thing shown in Ashes of Outland is the possible existence of a cult. Namely, the Rustsworn. Rustsworn Cultist, Rustsworn Inquisitor and Rustsworn Initiate are part of this supposed group. What do Old Gods love more than tentacles and giant eyeballs? A good old-fashioned cult. 

If that does not convince you, take a look at Rustsworn Cultist's shoulder pad.

Doesn't that look familiar to you? An eye. Huh, I wonder where we saw eyes on armor before...