Biting Gale (Yellow)

Ice Fusion

If this was fused, the attacking hero discards a card unless they pay

"Better to fight and fall than to live without hope." - Valgard Hoarfrost

Since defense reactions can’t defend in the defending window and must be played in the reaction window, you must pay Biting Gale’s cost to play it.
The attacking hero decides if they want to pay when biting Gale resolves (and becomes a defending card on the chain link)
If you have no cards in hand, you can still elect to discard a card instead of paying .

Fusion - Fusion is a new keyword that fuses one or more elements with an elemental card to give an additional effect.

You cannot reveal a card you are using to pitch to play the card. You pay resource costs before additional costs.
You may still play the card without paying the additional cost of Fusion.
You cannot reveal multiple cards to Fusion unless the card states you can (i.e a card with dual Fusion).
You cannot reveal a card that does not fit the criteria i.e you cannot reveal an Ice card to a Lightning Fusion card.
An Elemental card with Lightning Fusion is not a Lightning card/Element card. E.g you cannot fuse an Entwine Lightning with Entwine Lightning.
Defending with a card is not the same as playing and therefore you cannot fuse while defending with a card with fusion. Note, defense reactions are played in order to defend, paying their cost to do so. You can fuse a defense reaction card that has Fusion.

Cost2

Defense3