"The Grey"
The "Grey Invaders" or just "The Grey" as humans are calling them are the advanced race of aliens that have wiped out most of humanity. They use a variety of mech suits to do certain jobs. No human has ever seen out of their suits though one can occasionally glimpse their grey faces behind clear face shields.
Rumor has it the Grey don't have powers like the humans are seeming to gain, but their suits and advanced weaponry still make them tough to kill and dangerous. The humans they don't kill on sight are captured and taken away, never to be seen again.
The Grey outnumber the few million remaining humans almost 8 to 1 in most places. They are systematically harvesting the remaining oils and minerals that weren't easily extracted right after the massacre. Large camps can be seen surrounding well known oil and mining sights and smaller camps scattered about in between.
