The Dark Mirror

Whenever a creature you control dies, a target player discards a card.

{b}{b}{2}, {t}: Return a target creature card from your graveyard to the battlefield. It gains haste and “At the beginning of your upkeep, sacrifice this creature unless you pay 1 life.”

{u/b}{u/b}{4}, Sacrifice a creature: Search your library for Queen Nehelenia and put it onto the battlefield, then shuffle your library.