Polymerization

Although "alternate-art" versions of cards are common in Yu-Gi-Oh!, Polymerization is one of only two cards (the other is "Dark Magician") in the Japanese OCG where an "alternate-art" version has a different eight-digit passcode as well. The "alternate-art" form may be seen here.

Polymerization allows you to combine two Fusion Material Monsters into a Fusion Monster, making it one of the two cards you can use to summon them. To Special Summon the Fusion Monster, however, you must sacrifice the Fusion Material Monsters to the Graveyard.

The Special Summon counts as a Fusion Summon.