TCG Rulings

• This effect can activate during the Damage Step.^[1]

• If Wattfox is being treated as an Equip Spell that you control and it is destroyed, its effect will activate.^[1]

• If your opponent controls your Wattfox its effect will not activate when it is destroyed by either player’s card.^[1]

References

1. ↑ ^{1.0 1.1 1.2} Konami Gameplay FAQ: The Shining Darkness Sneak Peek -- Card Rulings (Version 1.0)