私立リディアン音楽院 is a Weiß Schwarz card from 戦姫絶唱シンフォギア SG/W19-070. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
Choose a 《Music》 character in your waiting room, and return it to your hand. You may choose a card in your hand, and put it into your waiting room. If you do, choose one of your characters, and that character gets +4000 power until end of turn.