Avell's Factory Guardian

Forge {4}{r} (You may cast this spell by paying its
forge cost and discarding an artifact card.)
{2}{r}, {t}, Sacrifice another artifact: Create an
X/X colorless Construct artifact creature token,
where X is the sacrificed artifact's converted
mana cost.
When Avell's Factory Guardian leaves the battlefield, return all artifact cards from your graveyard to the battlefield tapped.