A list of achievements reportedly outed from the upcoming Call of Duty: Ghosts includes nine rewards related to an unannounced Extinction mode.
speculates that based on the descriptions, and the recurring image of a non-human skull that it sounds like a four player co-operative mode similar to the popular Zombies scenarios in Treyarch's Call of Duty titles, possibly with some manner of alien as the adversary:
Achievement/Trophy descriptions like “Escape with all four players”, “Escape 1st time”, “Reach the exfil chopper with 1 minute and 30 seconds or more remaining on the clock” and “Complete all Extinction challenges and escape” all suggest the game mode is co-operative in nature and requires players to survive against unknown enemies, complete challenges, and escape the situation while possibly under a time limit.
“Get 50 kills with the electric fence and fire traps in a single game” indicates the game mode is based on survival while ”Make it to the cabin” and “Make it to the city” suggest that the play space might involve various areas that players will need to traverse and push through as the clock ticks.
Not much can be said for the enemies you may be facing, save for the logo that appears clearly on the “Completionist” achievement. If the shape of the skull is to be taken literally, might we have some sort of alien or monster apocalypse on our hands?
Aliens? Giant insects? Dinosaurs? Check out the images yourself
and make your own best guess.