I'm guessing that by "Essence" you mean "Edge," yes?
If so, then you can do whatever you like with it. It, and the Eternals, are intentionally vague in many ways - in particular their origins - so you can play. If you prefer, Spellbound
would make a fine option.
AEG = Alliance of Evil Geniuses, the Franchise front group du jour
. It'll be the last of the World on Fire
PDF releases and set up a campaign for you to run/modify as you will, and will also close out the CCG storyline for fans of that property.
There is no Eternals PDF planned.
Hope that helps clear things up.