Magic Rock "Heart Key"
From Ephinea PSO Wiki
Magic Rock "Heart Key" is a miscellaneous upgrade item in PSOBB. It can be used to obtain [Magical Piece], [Safety Heart], [Love Heart], and [Sweetheart]. It may be purchased from Paganini in [Gallon's Shop] for 50 [Photon Drops].
During Ephinea's [2nd Anniversary Event], the item was available for purchase for 20 2nd Anniv. Gold Badges from the Gold Badge Shop.