I'm trying to consider the circumstances leading up for the appearance of this new enemy, that I'm dubbing as "The Legion" (because their green weapons remind me of the Burning Legion from Warcraft 3).
Facts we know:
- Alternate Daedalus was destroyed 2 years ago by Replicators
This would mean that the Daedalus would have gotten into some sort of Replicator battle either during Season 3 (either in The Return - because Daedalus was sent to Atlantis to destroy Atlantis, OR in First Strike / Adrift because of their retaliation strike). It also seemed that by asking our reality to have the Daedalus, the Apollo could have been destroyed, or no new ships were being sent.
- Replicator's victory over Atlantis after fall of Daedalus
This could mean several things, one: no new ships being sent, and two: the replicator must have dealt with the wraith in the pegasus galaxy (remember that the Replicators were out there to wipe the galaxy of the wraith)
- How about the Replicators? Any possible relationship between the Rep versus the Legion?
I would think that the only reason these Legion would try to attack Atlantis is for their technology. Could it been that the Replicators are responsible for these new aliens? How about their technology? Could it also mean that these Legion come from outside the Pegasus galaxy?
My arguments are pretty weak, its stemming from one fact we know.