Kosi, Sultai Gravedigger

Deathtouch, Delve ( Each card you exile from your graveyard while casting this spell pays for {1})
Instant and sorcery spells in your graveyard have delve.
At the beginning of your upkeep put the top two cards of your library into your graveyard.
During each of your turns, you may cast an instant or sorcery card from your graveyard. If a card cast this way would be put into your graveyard, exile it instead.