If the ability triggers and the Urn isn't sacrificed (because it left the battlefield or changed controllers, for example), the exiled cards won't be returned to the battlefield
What are sealable inner sleeves for TCG
Essentially you get a choice of two 'sorceries' for the price of one, plus a value-generating creature if you wait till the late game
I could see a world where Tron starts to stretch for white mana at some point, as Krark-Clan Ironworks is both a scary matchup and a rising force in Modern, and Rest in Peace sounds like a powerful tool there, but I dont think were quite at that point yet
Personally, I think the card is good enough to see play whether you care about the two damage or not
Combo 6: Deadeye Navigator AND Cloud of Faeries AND Altar of the Brood This is another combo mill for the entire pod that is less than straightforward