Savathun, Witch Queen

Whenever you cast a Sorcery spell, you may exile
it instead. Cards exiled this way have flash and
may be cast from exile without paying their
mana cost.
Hive Creature spells, Sorcery spells, and Instant
spells you own have Convoke.
{2}, {t}: Sacrifice a creature, gain control of
target artifact until end of turn.