Inverted Iceberg // Iceberg Titan

When this artifact enters, mill a card, then draw a card. (To mill a card, put the top card of your library into your graveyard.) Craft with artifact {4}{U}{U} ({4}{U}{U}, Exile this artifact, Exile another artifact you control or an artifact card from your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.) Whenever this creature attacks, you may tap or untap target artifact or creature.