(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I - Urza's Saga gains "{T}: Add {C}."
II - Urza's Saga gains "2, {T}: Create a 0/0 colorless 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.