Raiders will come to your outpost every three days or whenever and for the different zones it has different effects. Green Zone: 2-3 Raiders, no headshots, small weapons like only melee and or pistols. Standard Zone: 3-4 Raiders, no headshots, same weapons from Green Zone but rifles are added. Dread Zone: Everything from Standard but the weapons are automatic and they have bigger melee weapons. Nightmare Zone: 5-6 Raiders, Headshots can happen, weapons are bigger like (snipers, launchers and Daybreak weapons), and heavy weapons.