Enchanted permanent has indestructible. (Effects that say "destroy" don't destroy that permanent. A creature with indestructible can't be destroyed by damage.)
{4}
Magnetic Mine
Artifact
Whenever another artifact is put into a graveyard from the battlefield, Magnetic Mine deals 2 damage to that artifact's controller.
{4}{W}{W}
Open the Vaults
Sorcery
Return all artifact and enchantment cards from all graveyards to the battlefield under their owners' control. (Auras with nothing to enchant remain in graveyards.)
{1}{G}{G}
Viridian Revel
Enchantment
Whenever an artifact is put into an opponent's graveyard from the battlefield, you may draw a card.