Amazoness Archers (DR1-EN151) [Dark Revelation Volume 1]

This card can only be activated when your opponent attacks and you control a monster on your side of the field that includes Amazoness in its card name, or is named Amazon Archer. All monsters on your side of the field become face-up Attack Position (Flip Effects are not activated) and as long as they remain face-up on the field decrease their ATK by 500 points. Your opponent must attack with all of these monsters this turn.