To enter Entna's secret chamber, at the title screen, highlight the "New Game" option, then press X, Y, B, X, Y, B, A. Alternately, beat the game after reading Etna's entries in her secret chamber. To enter Etna's secret chamber, press the two secret buttons in Laharl's Castle. The first button is located behind the throne. The second button is located inside the skull on the counter in RosenQueen's store. After both buttons are pressed, go to the room where Longinus, Ghoss, Stigma, and Gargo are found. Press A in the corner behind Stigma to reveal the door.