Best case scenario this is a one mana exile that hits any target
Similarly, if a face-down permanent leaves the battlefield, you must reveal it
This week we're seeing other Nadu cards like Umbra Mantle rising in price, too, but this is a less interesting case
If there's a cost with having that creature attack its owner, you aren't forced to pay that cost, so you may have it attack another player, attack a planeswalker an opponent controls, attack a battle an opponent protects, or not attack at all
Nice mana reduction over time, and when combined with the Chimes above that could be two mana made and discounts each opposing turn
Check out all the cards in our Rise Of The Floodborn Card List page