Advanced format ruling
Elemental HERO Air Neos
Card effect (current official text)"Elemental Hero Neos" + "Neo-Spacian Air Hummingbird"
This card can only be Special Summoned from your Extra Deck by returning the above cards you control to the Deck. (You do not use "Polymerization".) While your Life Points are lower than your opponent's, this card gains ATK equal to the difference. This card returns to the Extra Deck during the End Phase.
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.