Dusty Crevice

Dusty Crevice enters the battlefield tapped. Dusty Crevice does not untap unless you contol or have exiled 3 or more Legendary cards.
When Dusty Crevice enters the battlefield, you may pay {5}. When you do, choose target nonland permanent an opponent controls. Exile it.
{5},{t}, You may cast cards exiled with Dusty Crevice without paying their mana cast.