Could Anti Eternia be 1 of the 5 dimensions? I know the thread is about who came from where, but I seriously think Mattel should tap into this. Its way too cool for them to pass up IMO.
Here is an excerpt from "The Menace Of Trap Jaw!" Mini Comic. Notice the ghostly apparation of Grayskull. Skeletor even mentions how closely aligned it is to Eternia... And hey, going out on a limb, Trap Jaw could be the Anti Eternian Man At Arms with all the weapons knowledge & engineering and such. Maybe he lost his jaw after his facial armor failed or was destroyed. No, probably not.