When Hurkyl's Prodigy enters the battlefield, create a tapped
Powerstone token
(A Powerstone is an artifact with ": Add . This mana can't be spent to cast a nonartifact spell.").
Whenever Hurkyl's Prodigy attacks, you may pay
. If you do, Hurkyl's Prodigy can't be blocked this turn and it perpetually gets +2/+0.