Unrightful Sovereignty

As Unrightful Sovereignty enters the battlefield,
exile target creature, and all permanents attached
to it until Unrightful Sovereignty leaves the
battlefield. You may cast this cards for as long as
they remain exiled, and you may spend mana as
though it were mana of any type to cast that spell.
"Arthur is told prophecy by Merlin about a just-born
child that is to be his undoing, and so he tries to avert
the fate by ordering the killing of all the May Day
newborns"