Keiran, Necromantic Scholar

Whenever you cast an instant or sorcery spell,
you may sacrifice another creature with the same converted mana cost as that spell. If you do, copy
it. You may choose new targets for the copy.
When Keiran, Necromantic Scholar enters the battlefield, you may sacrifice another creature. If
you do, search your library for an instant or
sorcery card with the same converted mana cost
as the sacrificed creature, reveal it, put it into
your hand, and shuffle your library.