Illusory Grotto

Final Floor: B??F
Unlock Method: Random chance when you have no Reviver Seeds in your inventory
Initial Level: -
Maximum Teammates: 3
Items: Yes
Check Map: Yes
Opponents Able to Join: Yes

This dungeon only appears for a limited time. It often appears after having lost in a dungeon with no rescue. The level of Pokémon you encounter scale to the level of the dungeon you lost in and its size varies. It offers a myriad of rewards, specifically Reviver Seeds, Revive-All Orbs and Max Elixir.
The Pokémon you encounter depend on the dungeon you lost in

Illusory Grotto