Advanced format ruling
Chthonian Polymer
Card effect (current official text)Activate only when your opponent Fusion Summons a Fusion Monster. Tribute 1 monster to take control of that Fusion Monster.
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.