Somni, Watchful Alchemist

+2: Create a treasure token with {t}{1}, Sacrifice this artifact: Draw a card.
-4: Target opponent may sacrifice a treasure token. If they do, create two treasure tokens. If not, destroy target nonland permanent they control.
-10: Sacrifice any number of treasure tokens. The next X spells, where X is the number of treasure tokens sacrificed, cost no mana to cast.