Details
In The Crown Tundra, there's a new feature
where you can join with up to 3 players to venture into the Pokémon Dens. As you explore the caves in the area, you will find paths blocked by various Pokémon that have Dynamaxed.
To proceed, you need to defeat the Dynamax Pokémon to clear a path. However, if you are defeated, you will be sent out of the den.
Rental Pokémon
> Rather than utilise your own Pokémon in Dynamax Adventures, you instead use some Rental Pokémon. At the start of the journey, you can choose between 3 randomly selected Pokémon and the other players will do the same. Players take turns so you can co-ordinate better.
As you go through, you may catch all the Pokémon you encounter. When you do so, you can switch to them if you do so wish. When you exit the Dynamax Adventure, you have the capability of bringing back 1 of the Pokémon you caught.
These Pokémon can be shiny but won't appear Shiny when you battle them, only when you go to leave the Dynamax Adventures. While players may catch the same Pokémon, if it's Shiny it wouldn't be shiny for both players, it's decided by the player's game.
Link to all possible Pokemon that can be generated
Legendary Pokémon
> At the end of the den, you will often come up with against various strong Pokémon, these include various Legendary Pokémon including Solgaleo, Lunala, Mewtwo, Giratina and more. Defeat them and you will have a chance to capture them. You can only capture each Legendary once but will encounter them if you participate in other's raids.
If you fail to catch it, then you will be able to revisit it by selecting the path directly. Peonia will also sell you paths to Legendary Pokémon for 5 Dynite Ore.
Endless Dynamax Adventures
> There is also a special mode which will allow you and your team to go through the dens with more and more Max Raid Battles until you have lost a battle.
Path of Adventure
> As you go through the Dynamax Adventure Den, you'll have the opportunity to select certain paths. These paths provide different Pokémon of different types to fight before you get to the final Pokémon, a Legendary Pokémon.
These Pokémon can include fully evolved Pokémon and Alolan Forms.
Source:Serebii