Advanced format ruling
King of the Swamp
Card effect (current official text)This card can be used as a substitute for any 1 Fusion Material whose name is specifically listed on the Fusion Monster Card, but the other Fusion Material(s) must be correct. You can discard this card to the Graveyard; add 1 "Polymerization" from your Deck to your hand.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.