I was very confused how to access co-op when I started, but its actually easy.
ENDLESS Dungeon How to Play CO-OP
Here’s what to do:
- Complete/skip the tutorial.
- Go to the menu.
- Select CO-OP, either host a session or join your friends.
- Players need to be in the same region.
- The host will carry over the progression of the saloon/world, but each player will be able to level up their characters respectively.