Poisonous Viper

You can reveal this card in your hand; Special Summon it, or if your opponent controls no monsters, Special Summon it to their field in Defense Position instead. Once per turn, during your Standby Phase: Take 500 damage. If this card is banished, or sent to the GY by card effect: You can target 1 Set Spell/Trap your opponent controls; destroy it. It cannot be activated in response to this effect's activation. You can only use this effect of "Poisonous Viper" once per turn.