In game the Regi Trio are infamous for the difficulty in obtaining them. Exclusive to Ruby, Sapphire and Emerald the Regi Trio are obtained in a very complicated an elaborate manner which includes having to read Braille text. In order to unlock them you must first navigate the maze-like waters west of Pacifidlog Town to find a secret, underwater tunnel. This leads to an underwater cave with a Braille inscription reading "First comes Relicanth, Last comes Wailord". After placing a Relicanth at the top of your party and a Wailord at the bottom the sound of three doors opening is heard, indicating the opening of the three tombs of the Regi Trio. Regice's tomb is located on the ocean Route 104, northwest of Dewford Town. Once inside, you must simply stand in the middle of the room and wait a couple of minutes; the door to the back room will open and inside is Regice, found at level 40.
The Regi Trio also have an important use in Diamond and Pearl; namely awakening Regigigas. Regigigas is another legendary found at the base of the Snowpoint Temple in Snowpoint City. Regigigas appears as a statue in the game and will only awaken if the three members of the Regi Trio are in the player's party. The Regi Trio, as with all other Pokemon from the previous games, are able to be obtained in Diamond and Pearl through use of the Pal Park.