King of the Swamp (PSR) [SBC2-ENI23] Prismatic Secret Rare

This card in your hand, field, or GY can be used as a substitute for any 1 Fusion Material whose name is mentioned on the Fusion Monster Card, but the other materials must be correct. You can discard this card to the GY; add 1 "Polymerization" from your Deck to your hand.