Elemental Hero Dark Neos

"Elemental Hero Neos" + "Neo-Spacian Dark Panther"This card can only be Special Summoned from your Fusion Deck by returning the above cards from your side of the field to the Deck. (You do not use "Polymerization".) You can select 1 face-up Effect Monster on the field if 1 is not already selected by this card. While you control this face-up card, the selected monster's effect is negated until it is removed from the field. (You can select up to 1 monster at a time with this effect.) This card returns to the Fusion Deck during the End Phase.