3 months ago - Crater Creator - Direct link
There is a game stage system that scales risks (e.g. zombies) and rewards (e.g. loot) up and down depending chiefly on your player level. When multiple players are in physical proximity they get a combined game stage value and the game adjusts accordingly, from quests to Blood Moons. In theory this serves up a balanced experience for any number of players, up to the officially supported limit. I say in theory only because I haven't personally been big on multiplayer for some time.