Continuous-like. Ignition-like. Trigger-like. Continuous. While a Gravekeeper's monster and/or Necrovalley are on the field, all monsters your opponent controls lose 500 ATK/DEF. Once per turn, during the Main Phase, if you do not control a card in your Field Zone: You can activate 1 Necrovalley from your hand or GY. If this card is destroyed by your opponents card effect and sent to the GY: You can Set 1 Necrovalley Spell/Trap from your Deck, except Necrovalley.