Once per turn, during your Main Phase, if you control this monster on the field, you can equip it to a face-up monster on your side of the field as an Equip Spell Card, OR change it back to a monster in face-up Attack Position. When equipped to a monster by this card's effect, that monster will not be affected by the effects of Spell Cards controlled by your opponent. (1 monster can only be equipped with 1 Union Monster at a time. If the monster that this card is equipped to is destroyed in battle, this card is destroyed instead.)