You can send 1 "D/D" or "Dark Contract" card from your hand to the Graveyard, then target 1 card on the field; destroy it. You can only use this effect of "Dark Contract with the Valkyrie" once per turn. All Fiend-Type monsters you control gain 1000 ATK during your opponent's turn only. Once per turn, during your Standby Phase: Take 1000 damage.