Transmute Artifact

Sacrifice an artifact. If you do, search your library
for an artifact card. If that card's converted mana
cost is less than or equal to the sacrificed
artifact's converted mana cost, put it onto the
battlefield. If it's greater, you may pay Variable
Colorless, where X is the difference. If you do,
put it onto the battlefield. If you don't, put it
into its owner's graveyard. Then shuffle your
library.