Hurkyl's Prodigy is a uncommon Creature — Human Soldier card from Alchemy: The Brothers' War (YBRO), collector number 4.
When Hurkyl's Prodigy enters, create a tapped Powerstone token. Whenever Hurkyl's Prodigy attacks, you may pay {2}. If you do, Hurkyl's Prodigy can't be blocked this turn and it perpetually gets +2/+0.