The Phantom Knights of Shadow Veil

Card text

Target 1 face-up monster you control; it gains 300 ATK/DEF. When an opponent's monster declares a direct attack while this card is in your GY: Special Summon this card in Defense Position as a Normal Monster (Warrior/DARK/Level 4/ATK 0/DEF 300). (This card is NOT treated as a Trap.) If Summoned this way, banish this card when it leaves the field.