You can still activate the second ability while Urzas Saga remains on the battlefield
// Vigilance On turns where the effect of Summon: Yojimbo's second or third chapter ability is applying, your opponents can choose not to attack with a creature that must attack if able as long as there is no other player, planeswalker, or battle for that creature to attack that wouldn't require a cost
Chart shows the price of Perrin #160 at the end of each month going back as long as we have tracked the item.
We believe that having a well-rounded party (team) that represents and reflects the world around us provides a critical advantage by allowing WotC to build incredible game worlds that everyone can see themselves in, the company writes in the job description, which was posted in July
Its not hard to engineer a situation like this, and if you do the card essentially becomes a fight spell that can also target players and planeswalkers
Seriously awesome artwork on this one, though