Surprise!

A.K.A. Ambush tribal. Ambush and Fast Spells are very powerful tools that get better as their concentration in a deck increases. There are two main reasons for this:

1) Consistently playing at the end of your opponent's turn lets you play with more information available.
2) Consistently having Ambush response windows gives your opponent less information about your hand.

Argent Depths is the first set where I finally feel like we have a reached a critical mass of good Ambush units to make this theme legitimate. Most of the card choices are probably fairly self-explanatory, so I'll only focus on the ones that are new or might need some additional context.

In this deck, Desperate Courier is basically a better version of Initiate of the Sands. It doesn't die to all of the "free" 1 health removal like Vara's Favor or Blightmoth, which is extremely relevant in today's meta, and it's even more effective when you are playing multiple cheaper cards in the same turn. In addition, Plunder helps a great deal to smooth out power issues on either the screw or flood side of the coin. Speaking of Plunder, Desert Alchemist is a very powerful set piece for answering aggro and midrange threats alike that just happens to also fix up draws; I expect this to become a staple in a wide range of decks.

Ayan, Dark Conduit is a great roadblock for aggro, and his attack trigger makes it possible to play Xumucan, the Surveyor on curve even with ramp! Once his 6x influence ability is active, he can really disrupt an opponent's plans—turning off popular lines of play like Defiance or fast card draw—and ramp you into some pretty massive turns. More often than not, the ability actually results in him just being removal bait, which is great considering the other threats we have further up the curve. It's worth noting that, if he becomes popular, he's also extremely effective at countering this deck :(

Gentle Grazer is not new, but needs to be called out due to a couple of critical interactions this deck's pilot needs to be aware of. First, we are running Annihilate, which means that dropping him against an empty opponent board has a unfortunately high chance (3/14 or ~21%, if you haven't drawn any of your 1- or 2-cost cards yet) of being forced to kill one of your own units. Now, in the current meta, I have found the case where there isn't a good Annihilate target fairly rare, but it can happen, especially against control; pilot beware. Second, and more positively, Desperate Courier reduces the cost of cards in all zones, which means it expands the range of cards that Grazer can hit! With just one Courier, you might hit an Ayan (or a Banish, which comes with the same warning applied to Annihilate), and with two Couriers out, Grazer can even hit itself!

Xenan Temple has nothing to do with Ambush or Fast Spells, but it's a really good card that helps grind against control and can put some games out of reach if you are already ahead, so we run it.

Last but basically the opposite of least, Touvon, Skybreak Giant brings a huge amount of power to the top end of the deck. His activated ability does take away from your available to use on your opponent's next turn, but the value is absolutely worth it, and you will often find that an activated Ayan, Dark Conduit leaves you with power that needs a sink anyway. I think this guy is what transforms this deck from meme to dream.

For the power base, we are running as many dual powers as possible to hit our double shadow influence on turn 3, while still running all Time sources so that we can more consistently play Xumucan, the Surveyor on curve, and running enough Sigils to keep our Seats undepleted most of the time. Xenan Cylix is basically just a free drop in that you can almost always play activated to help you grind out your opponent. 29 sources plus Courier plus access to Plunder has felt pretty smooth, but I will be first admit that I am generally terrible at building power bases, so a better deck builder than I could probably improve it.

The Market is pretty flexible, and should be tweaked based on what you see in your own meta pocket. I see Icaria, First Reaper in close to half of the decks I play against, so I run Swirl the Sands and Gnash, Desert Prince as direct answers. Swirl the Sands and Vara's Choice are both flexible answers to other cards as well; notably, Swirl being fast means that you can both fetch it and play it immediately at the end of an opponent's turn, provided you have the power (and Courier helps with this line!). Last Chance is pretty much always a good Market option, and it synergizes well with Xenan Temple, on occasion. Dizo's Office is a good stabilizer/finisher when you can afford it and don't need a more immediate answer.