Ross Merriam posted some great content on SCG last week outlining a UR Prowess deck for Oath of the Gatewatch Standard. You can see the deck in action here. The deck was picked up by a number of players for the Atlanta Open, including Dalton Ozman who piloted the deck to a Top 8 berth.
This deck falls into my wheelhouse exactly, so when I first saw these lists I was hopeful that they'd be great. There are definitely weaknesses here, specifically being that Expedite and Slip Through Space are conditional cantrips that don't even offer card filtering. As a person who has spoken ill of Gitaxian Probe on more than one occasion- a card better than both of these cards by a fair margin- I'm somewhat skeptical of this deck's staying power. That said, I want this deck to be great so I've been investing some time into polishing it.
Given the weakness of some individual elements of the deck, I find it peculiar that Painful Truths was only a one-of in Mirriam's list and a sideboard card in Ozman's. These decks certainly have explosive potential, but Treasure Cruise as the only good draw spell in a deck that needs to aggressively trigger prowess strikes me as a mediocre mix given the comparison to Atarka Red. If I need to build up for a delve spell I'd rather it just killed my opponent.
That said, tuning up the manabase to fully support Painful Truths adds a level of robustness that is great for decks that are this efficient. The life loss is at its most trivial in a deck that's just great at killing opponents. The other benefit of committing more to black is that we get to play a bunch of Duress. Duress helps build up delve for Treasure Cruise while making sure that our Slip Through Spaces and Titan's Strengths resolve. Hitting ramp spells out of Eldrazi Ramp and Rally the Ancestors is a nice bonus.
I'm not in love with Fiery Impulse in the maindeck, because I think for game one you just need to be a machine focused on getting them dead. This is the list that I intend to test when Oath launches on MTGO.
A lot of comments on Merriam's content have been that Jace has no place here, which I assume is mostly coming from players who want to find reasons not to play Jace because of its price tag. I will grant that Jace might not be the best fit for the deck, but considering that this deck just wants to keep casting spells, the looting Jace provides and the ability to flash spells back both shine here. It's also just another body to target with your cantrips when you don't find any of your 12 threats- a rather low density.
If Jace is wrong and/or out of your price range, I think you want to fill that space with at least two of the four slots going to creatures. Unfortunately, all of the options come with their own downsides. Zurgo Bellstriker is a solid enough card, but I don't think it shines in a shell that only plays Titan's Strength to make it do more than attack for two. Odds are you want to fill this slot with something with prowess.
I'm fairly certain that this deck really wants this slot to cost two mana and have two power. Trying anything else just might not be efficient enough, though Shu Yun is an option that that would be interesting to try. Seeing as this deck is always casting spells and always attacking, I'm inclined to believe that Mage-Ring Bully is the pick. I'm sure you'll catch some crap for battling with it, but that never stopped me from crushing people with it in Origins limited.
I'd flesh the rest of the deck out with one or two copies of Magmatic Insight. I wasn't kidding about wanting that loot effect. According to the comment section on the Vs. Video linked above, Merriam played one copy this weekend and it was great. It's superb at fueling Treasure Cruise, and is a one mana cantrip that does more to build a hand than your other cantrips- provided that you have a land to pitch.
I love the idea of this deck, and I hope that it just ends up being great. If it is to be great, then I'm firmly of the belief that Painful Truths is its future.