Spirit of the Six Samurai (SDWA-EN012) [Structure Deck: Samurai Warlords]

Once per turn, you can equip this card to a face-up "Six Samurai" monster you control, OR unequip it and Special Summon it in face-up Attack Position. When equipped to a monster by this card's effect, that equipped monster gains 500 ATK and DEF. When the equipped monster destroys an opponent's monster by battle, draw 1 card. (A monster can only be equipped with 1 Union monster at a time. If the equipped monster would be destroyed, destroy this card instead.)