Talk to the Ravaged Battlefield Guard, and select difficulty.
*Clear at least once to open the next difficulty level.
*To unlock Master; clear Veteran.
*To unlock Extreme; clear Master.
*To unlock Hardcore; clear Extreme.

Select Room after selecting the difficulty. You can create, select, or search Rooms, and change the deck set from here.
Set your Challenge Deck and create your own Room or select and enter other Adventurer’s Room to challenge the Ravaged Battlefield.

How to set a password
You can set a password for Rooms above Veteran level.

After creating the room, you can enter the Ravaged Battlefield. At the moment you enter the Ravaged Battlefield, one Ravaged Battlefield Ticket is consumed and the time limit according to the difficulty level you selected starts ticking.
You can enter locked spaces by defeating Bosses, the Beasts standing in front of each space. The Ravaged Battlefield is cleared once the end-boss is defeated by you or other Adventurers who entered the room.
Also, rare materials are collectible inside the Ravaged Battlefield.
The effect of items increasing Collection Rate is applicable to materials achieved in the Ravaged Battlefield Dungeons. Use it wisely!

*Caravans can’t go into dungeons, but some of their features like warping can be used on the Minimap.
*Boss spawn locations are random.
*Up to 21 people can fit into a single room, but only up to 3 can challenge a given boss at a time.
*Only end-bosses will maintain their present HP amount from battles with other players.
*The moment an end-boss has entered battle for the first time, the room will no longer be joinable outside of the room search feature.
*While you do receive Contribution for defeating bosses and dealing damage in battle, this does not have any effect on the rewards you receive at present.
*Rooms with passwords are not displayed on the Room List. To enter these Rooms, use Search Room function.

At maximum difficulty, your units won’t recover HP after the battle. So search the dungeon carefully.
If all the units in your deck are knocked out in a Ravaged Battlefield dungeon, you’ll be changed over to a Spectator Mode.

What is a Spectator Mode?
If you are in a Spectator Mode, you can’t attack the Beast but still can get reward items.
To leave the room, touch the warp near to your respawn point or use warp function from the Minimap.