11 Pokémon can be caught at Underground Ruins in Unova.
Deep within the Clay Tunnel lie the Underground Ruins, where Regirock, Regice, and Registeel — the legendary giants — can each be encountered, determined by whichever Key is active. At first, the chambers offer only clues to unsealing Regirock's room, the available hint changing with whether the sun or moon is out, but meeting the conditions turns the great door into a gateway leading to Regirock's chamber and any others unlocked by Keys. Opening the Rock Peak Chamber involves walking six steps down and nine right from the panel before the door, then pressing the A-button.
