Heavy Mech Support Armor (SDKS-EN004)

If this card is Normal Summoned: You can target 1 Union monster in your GY; Special Summon it. Once per turn, you can either: Target 1 Machine monster you control; equip this card to that target, OR: Unequip this card and Special Summon it. Your opponent cannot target a monster equipped with this card with card effects, also if the equipped monster would be destroyed by battle or card effect, destroy this card instead.

Machine / Union / Effect, Structure Deck: Seto Kaiba