I was playing against Jace, so I played Thalia in order to raise the cost of Jace’s spells by 2. On his turn he played Multiverse Mind and drew a bunch of cards. All of the cards he drew from the deck only cost him 1 mana. They did not receive the +2 penalty. According to how the text of Multiverse Mind and Thalia’s debut reads, all of those cards should have cost 3.