Having now seen their in-game introduction (in a gameplay video, I don't have the game myself): This doesn't make any sense. Sure, I can see where an existing group of "off-grid" ADVENT could go around "recruiting" by (somehow) non-fatally skulljacking their former comrades, but how would such a group ever get started as an independent entity in the first place? There can't have been some "first defector" who arrived at the conclusion on his own, not with the ADVENT psionic hivemind enforcing loyalty. They would only make sense as an adjunct to one of the other groups—most plausibly, given their technical resources, XCOM themselves; they don't make any that I can see as an entirely separate, self-contained faction.

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.