The Nightosphere Amulet is a Weiß Schwarz card from Adventure Time AT/WX02-070. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
If you do not have an 《Ooo》 or 《Nightosphere》 character, this card cannot be played from your hand. You may choose 1 of your characters with "Marceline" in its card name, and put it into your waiting room. If you do, choose 1 "Marceline: Filled with Chaotic Evil" in your waiting room, and put it on any position of your stage. Put this card into your memory.