That's Orim's Chant in a nutshell: good for stopping an opponent in the middle of his combo while he has a bazillion mana floating and damned if he isn't going to take mana burn and die, but don't you just wish it was a cantrip
When time began, the Ur-Dragon began with it
With the addition of the Hallowed Fountain dual land, which allows you to now efficiently splash for the blue color, this deck has gotten even more resilient due to its ability to add counter spells after sideboarding, protecting your fragile creatures from board wipe spells
Reprieve replaces itself, which in a white-blue or white-blue-x deck might mean a hard counterspell, which is going to happen and is going to be such a beating
You can get both Urborg and Cabal Coffers
It has historically lagged behind Blastoise and Charizard in price, but the gap has been narrowing as collectors seek to complete the trio