Ever play DMZ in the new CoD MW2? Its gonna be sorta like that, but instead of being a game-mode Marathon is entirely an extraction-shooter game (better examples would be: Escape from Tarkov, Vigor). I would assume it has Enemy NPC Aliens for PVE elements based around the lore, while being mostly a PVP-themed extraction-shooter game... [spoiler]I mentioned the game Vigor, (if I remember it correctly) mainly because although it may claim to be a looter shooter it is a F2P PVP type of game, which seems to fit the extraction-shooter mantra of get in, fight, get loot, extract.[/spoiler]