Research is shared between players when choosing to play on the same team. If both players research the same item, the time it takes is reduced. When one player discovered a technology, the other gets it as well.Players share the benefits of landmarks, ruins, and other discoveries on the map.Players share the map. Diplomatic options are available as well to trade resources, gold, and units.Co-Op is played in multiplayer with each player picking to join the same "team." It's assumed a balance of 3 players vs 3 AI are chosen, but you can weight it to 3vs1vs1vs1 or 3vs2 or 2vs1, etc.
Four player co-op is available in all game modes and types including a story mode and an unlockable survival mode. While you can't drop in to a game, you can drop out and not break the session if you aren't the host.
Terraria is a world building open ended side scrolling action game. Think of it like Minecraft in 2D.
Infestation is an online co-op swarm mode. 4 players can join together to take on increasingly difficult waves of enemies.
Team up in a PvE experience with friends.
New Co-Op game mode ‘Assault’: Challenges players to defend a strategic location against waves of enemy ground vehicles or aircraft. For tankers, combat is fought tank to tank on the ground, with the ability to temporarily support teammates in attack aircraft or bombers. Pilots are tasked with maintaining air superiority over a zone by fending off enemy bombers approaching from all directions. As each successive wave is stronger than the previous one, players have to work together to hold out until the end, upon which they will receive well-deserved rewards.
7 Days to Die supports up to eight players on a server. Players can setup their own private servers for a multiplayer session and set options like friendly fire and difficulty
Two players can take on the entire campaign together online. Co-op mechanics include the ability to revive a fallen comrade or spot enemies with your binoculars, marking their locations for both players. Other co-op modes include Killy Tally (survive 10 waves of enemies), Bombing Run (hunt for vehicle parts before time runs out), and Overwatch (one player snipes while the other spots enemies and carries out objectives).
Players guide their ships around a procedurally generated world, solving quests, fighting pirates, and trading cargo all the while.
Join forces with other online players as you battle for survival in a dangerous world filled with dinosaurs.
Up to three other players can join the host player as farmhands. Farmhands can do almost anything the main player can do. They can farm, mine, fight, fish, forage, marry NPCs and take part in festivals. Each player has their own inventory. When a farmhand is not connected, their inventory can be managed through a chest in their cabin.
NOTE: The co-op feature is not currently implemented into the game. It is anticipated there will be a beta later this year with a full release of the feature in 2018.