It’s not that different than how’d you implement a multiplayer game. Take a real time strategy game (not quite the best example). But if you’re a client, you’d only be concerned with those you can see on the battlefield, especially if there’s a fog of war.

Anyways, you can also do things naively. Some RTS games just handed down the entire state to every client and let them figure it out. You can see how people would take advantage of that to strip away fog of war during online matches.