Jpastor, the Creator

Jpastor's power and toughness are each equal to the
number of artifacts you control.

Whenever you cast an artifact spell, you may
sacrifice an artifact. If you do, reduce that spell's
mana value by the mana value of the sacrificed
artifact.

{x}{x}{x}, {t}: Create a custom artifact card with
mana value X and put it into your hand.
(It must be balanced.)