Elemental Hero Electrum (MDP2-EN001) - McDonald's Promo Series 2 Limited

"""Elemental Hero Avian"" + ""Elemental Hero Burstinatrix"" + ""Elemental Hero Clayman"" + ""Elemental Hero Bubbleman""
This monster cannot be Special Summoned except by Fusion Summon. The Attribute of this card is also treated as WIND, WATER, FIRE, and EARTH. When this card is Fusion Summoned, return all removed from play cards to their owners' Deck(s), then shuffle those Deck(s). Increase the ATK of this card by 300 points for each monster on your opponent's side of the field that shares an Attribute with this card."