These are the multiplayer versions of some advent hero dungeons. All of them has a daily attempt limit of 10. Instead of the chance to get an advent hero, you’ll obtain their spirit shards instead. These spirit shards can be traded in the Town’s Laboratory building. If you’re using one of the recommended heroes for the dungeon (varies per dungeon), you may still get the chance to obtain advent hero as a bonus reward.
If you’re joining someone’s party, you have to select your character and set the status to ready. Every member of the party must set the status to ready before the leader can start the battle. If you’re the party’s leader, you can add up to three more heroes you control in the party. The last slot still needs to be filled by another player; otherwise, you won’t be able to start the battle.
During the battle, you can only issue commands to your character. You have 10 seconds to issue a command; otherwise, your character will just automatically perform a basic attack. If your character has been knocked out, you can still cheer for the surviving player by tapping the prompt on the screen. This will allow the surviving player to recover a bit of HP.
Finally, you can also enter the Searching for Treasure Co-op dungeon. This is practically the same as the other advent dungeons but with a forgivable difficulty and Evolution materials (mons and 4* R-heroes) as possible rewards for using recommended heroes.