Rift Rupture

This spell cannot be countered if cast during your
main phase.
In addition to paying the normal cost of this card,
lose 5 life. Exile each permanent of converted
mana cost {x} or less.
A player may pay life equal to the mana cost of an exiled card of theirs that has been exiled this way
as a sorcery. Only one card may be brought from
exile this way during each controlling players turn.