Trumpet of Cernunnos is a Weiß Schwarz card from The Seven Deadly Sins SDS/SX03-075. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
Choose 1 of your 《Britannia》 characters, and that character gets +2000 power and the following ability until end of turn. "【AUTO】 When this card's battle opponent becomes 【REVERSE】, you may choose 1 character in your waiting room, and return it to your hand." Put this card into your stock.