(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 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.