Storm off with Aetherflux Reservoir. This deck got some attention early on, but that kind of fell by the wayside after competitive players learned that it wasn't very reliable and once Herald of Kozilek rotated it died completely. However, Dominaria dropped a few new cards that I believe make this deck a viable choice, at least at FNM.
Foundry Assistant and Jhoira's Familiar decrease the cost of every spell in the mainboard that costs more than one mana except for Paradoxical Outcome. Cast your eggs early to keep your hand full and hit land drops (helped tremendously by Artificer's Assistant) and bounce and re-cast them later with Paradoxical Outcome. In almost every case, the Familiar is strictly worse, but still good enough for a playset to find a home in the build. This is the primary reason this deck can be played again, since it replaces Herald of Kozilek. It costs more than the eldrazi and is less likely to survive being used as a blocker, but can have its cost eventually reduced further, can stop threats in the air if we really need it to, and doesn't require us to play a second color. All in all, I think the two cards are about even in the Standard Storm deck.
With one Reservoir on the battlefield, we need to cast a maximum of ten spells to win the game, but this can be lower if we have more than five life or have multiple Reservoirs in play. We have a bunch of eggs to make sure we can get to that storm count even if we only manage to bounce four or so permanents with Paradoxical Outcome.
Prophetic Prism: The best one, since it also fixes our mana, letting us pay for Metalspinner's Puzzleknot's ability and allowing us to chain paradoxical outcomes if we have at least two Powerstone Shards.
Metalspinner's Puzzleknot: Losing a life is kind of annoying early on, but if you actually start to combo off it's irrelevant. Being able to pay three for another draw is also nice.
Glassblower's Puzzleknot: It's unfortunate that we can't actually draw with this one, but scrying two is almost as good, or even better if we're still looking for one of our two main combo pieces. The energy also helps keep our Aether Hubs online, and again the option to sac it is occasionally quite helpful.
In addition to these spells, we have a few more ways to up our storm count while also covering other bases.
Metalwork Colossus: This is usually free by turn five, keeping us alive until we go off and serving as an alternate win con. Bouncing and replaying it with Paradoxical Outcome gets another card drawn and storm count too. Also, while it doesn't come up too often, if we have one in our graveyard and one on the battlefield along with a few other artifacts we can sac them back and forth to get a few more spells cast at the end of a turn.
Powerstone Shard: While I initially tried a playset of Gilded Lotuses, I quickly realized that the Shard is better in every relevant way. This is another permanent we can bounce and replay when we go off, and once we have at least two they can allow us to draw our entire deck in one turn by providing the mana (made blue with the Prism) for another Paradoxical Outcome after each time they're played. Of course, we never NEED to draw our whole deck, but it's a fun thing to worth noting.
Opt is perfect for smoothing out our early game draws and hitting land drops. I considered splashing green for Adventurous Impulse, but it's not that much better and the mana would have gotten a bit inconsistent, especially since Zhalfirin Void is a definite four-of. Aether Hub exists instead of more Islands to give us four more black sources for cracking a Metalspinner's Puzzleknot, and Glassblower's Puzzleknot's energy makes it essentially risk free. Inventor's Fair has obvious value, but in playtesting I actually sacrifice it very infrequently, so there's only one to avoid the nightmare of missing land drops early on due to the legend rule.
And, that's about it… except for Artificer's Assistant. This guy deserves some serious credit, and is usually a better turn-one play than Opt. We can cycle through more than half our deck with it before we even start to go off. With only seven cards in the mainboard not triggering its ability, it gets us a crazy amount of value; so much so that I believe it's correct to run it over the likes of Reverse-Engineer. I'd like to find a place for this cheap draw-three, but I don't think it's better than anything else. I've also thought about Panharmonicon, but it feels unnecessary because the deck already draws enough cards. Funnily enough, when I was including Gilded Lotuses I tried out a one-of Lich's Mastery. Lich's Mastery is playable because it's almost TOO good at drawing cards, decking us before we gain enough life to win. But it's way too slow for us, and also unnecessary.
I haven't given the sideboard as much thought as the mainboard, but I think it's pretty solid. I'm very open to suggestions for optimizing it though, and different players will want to change it up to better fight their local metas.
Baral's Expertise: In case there's a Damping Sphere or some other permanent stopping us from going off, this can deal with it before immediately leading into a Paradoxical Outcome. Also a general catch-all to buy us a few more turns against extreme threats.
Dispel and Metalic Rebuke: Control is certainly a very hard matchup. These let us fight a fight. Also ok against the red deck.
Padeem, Consul of Innovation: Our opponents are going to side in any artifact hate they have after game one. Padeem slows us down a bit but protects us, is an extra draw engine, and conveniently gets reduced by Jhoira's Familiar.
The Immortal Sun: Another way to fight against control. I've always believed that UW was the best shell for control in Kaladesh-legal Standard, and my guess is that Teferri, Hero of Dominaria will now finally convince everyone else. The Immortal Sun almost always lets us go off the turn after we play it with its cost reduction effect.
That's the deck so far. I clearly devoted most of the sideboard to fighting against control, and that's because I believe that it's the only matchup where it's worth going off our plan a little bit to fight. Against every other deck, I think our best game plan is to just race them. Right now, turn five wins are reasonable every once in a while with very good draws, but the deck usually wins turn six or seven. I'd like to get it to a more consistent turn six victory, baring significant disruption from our opponent. While Artificer's Assistant really helps, the one missing piece seems to be a way to get to Paradoxical Outcome more consistently. Glint-Nest Crane also seems reasonable at finding the Resevoir, but not better than an Assistant turn one or two. Any suggestions would be great, and if anyone decides to take it for a spin please comment on how it works for you!
UPDATE
So, it turns out that Jhoira is busted in a deck full of artifacts. Sometimes we can win the game without casting a single Paradoxical Outcome, especially if we have one or more Artificer's Assistants. She definitely provides the consistency I was looking for, and in play testing the deck goes off on turn six almost every time now.
To account for the red splash, there's now a playset of Spire of Industry. I also took out the Metalwork Colossuses to make room for her, because she seems much more useful. Prophetic Prism is even more important now. The three legendaries are also accompanied by a single Mox Amber.
Because it can be so important to have cost reducers, the deck now includes one Trophy Mage to grab Foundry Inspector, or perhaps Powerstone Shard. In addition, I've decided that the counter spells are enough of a sideboard package for control and have replaced The Immortal Sun with Battle at the Bridge, which helps race the red deck and also works towards our plan.
