Memory Harvester

Whenever an opponent discards a card, they mill
a card.
{3}, {t}: Each player discards a card. Then, if an
instant or sorcery card is discarded this way,
create a colorless Memory artifact token with
"{t}, Sacrifice this artifact: Target instant or
sorcery card in your graveyard gains flashback
until end of turn. The flashback cost is equal to
its mana cost."