Nightmares and Daydreams

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
[I] [II] [III] Until your next turn, whenever you cast an instant or sorcery spell, target player mills cards equal to that spell's mana value.
[IV] Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.