Similar to Dark Souls, but better overall.
You need to send distress signal and someone will join. If you play with friend, set password, so only friend can join.
Coop will be available after first boss.
Player can join you, if you didn't kill map boss.
You can join other players only on maps, that you already unlocked.
Dungeons (Depths) has different matchmaking. So both players must be here in order to play.

Originally posted by It is my CAT:

Similar to Dark Souls, but better overall.
You need to send distress signal and someone will join. If you play with friend, set password, so only friend can join.
Coop will be available after first boss.
Player can join you, if you didn't kill map boss.
You can join other players only on maps, that you already unlocked.
Dungeons (Depths) has different matchmaking. So both players must be here in order to play.

do both players recieve xp? what about loot, drops from mobs/bosses? if i understand right, only host gets loot?
i finished cathedral and now in frozen map, im thinking about buy game for family member to play toghether, i doubt she will be wanting to progress alone.

There is an option you can enable so you can go to any map. The load will be longer because need load it's loadout though, so it's highly recommended for both players be in the same map. Aside of that, monster drops goes to both players and both get mist from each defeated monster. The only difference is, if a guest is defeated, they not lose their mist, only the host. Also, for each boss defeated, both players get medals, and you need a high amount for an archievement (and max coop level). That includes each depths miniboss, so you can get 3-4 medals each depth cleared. On that note: if the main depth boss is defeated, no matter if minibosses are still there, the guest is kicked and need visit the mistletoe to respawn the enemies and keep going.

ok, thanks for answers.

Should add, there's a mod that allows you to join another player regardless of whether or not they've beaten the boss. But both players must have it. https://www.nexusmods.com/codevein/mods/192