Ranshi, Forsaken Shadow

Delve (Each card you exile from your graveyard
while casting this spell pays for 1.)
Skulk, deathtouch
Whenever Ranshi deals combat damage to an opponent, each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost. (You may
cast this card from your graveyard for its flashback
cost. Then exile it.)