They Who Know Nothing

When They Who Know Nothing enters the battlefield, exile a non-land permanent with X converted mana cost until it leaves the battlefield.
This card becomes a copy of that card, except its
name is They Who Know Nothing, is a legendary Creature in addition to its other types, is indestructible, and has the ability
{t}, sacrifice this card: Each opponent sacrifices all
non-land permanents that share a type with They
Who Know Nothing.
Nothing will survive!