(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)

I: Urza's Saga gains ": Add ."
II: Urza's Saga gains "2, : Create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control.'"
III: Search your library for an artifact card with mana cost 0 or 1, put it onto the battlefield, then shuffle.