"The Abandoned" is what the surviving humans call themselves, at least a big part of them. Since not everyone is happy that big darn heroes left to pursue after the aliens instead of staying with them. Because humans. 

The players will join a sort of task force initiated by a major surviving corporation to find, reverse-engineer and apply alien tech to restore the world. Along the way, there will be self-proclaimed messiahs, cults, warlords gangs and various other stuff that is very far away from human unity.