Exarion Universe (BP01-EN126) - Battle Pack: Epic Dawn 1st Edition

You can only activate this effect during a Battle Step of your turn. Decrease the ATK of this card by 400 points, then during battle between this attacking card and a Defense Position monster whose DEF is lower than the ATK of this card, inflict the difference as Battle Damage to your opponent's Life Points. This effect continues until the End Phase of the turn this effect is activated.