It gains "At the beginning of your upkeep, if this card is exiled, remove a refine counter from it" and "When the last refine counter is removed from this card, if it's exiled, you may cast it
If they cant discard a card, they must mill a card instead and skip the draw
Skyclave Apparition Meanwhile, Skyclave Apparition is also quite powerful in aggressive decks, though for very different reasons
Outside of removal, there's other powerful spells like the game-ender Exsanguinate, and the value engine Lingering Souls, both of which work well with Y'shtola's abilities due to being greater than mana value 3 when cast
The effect doesn't wear off until just before your next untap step (even if an effect will cause that untap step to be skipped)