Let's start with the individual cards.
Aether Vial-it's a powerhouse of a card. An Aether Vial on one is the most powerful start from this deck. The mana it creates over the course of a game is often upwards of seven or eight.
Things that can come from an Aether Vial activation are: draw step
Tidehollow Sculler, Leonin Arbiter in response to a fetch, main phase
Thalia, Guardian of Thraben to keep your opponent off of multiple noncreature spells on their next turn (more specifically until Thalia dies), removal in Wasteland Strangler, flickering away a tron land in the form of endstep Flickerwisp. Most of the time, it's correct to take
Aether Vial up to three because that's where most of the more impactful creatures in the deck are. There are, however, some exceptions. If you have mostly two-drops in hand, it might be worth it to leave it on two. It all really just comes down to what creatures are more valuable to you, and which creatures you can cast. The only case where you should tick it up to four is when you have a Thought-Knot Seer in hand, can't cast it, and don't have any three drops you want to vial in beforehand. Note: you can vial in a three drop in response to the trigger, then tick it up to four.
Next, we have: Path to Exile-the best removal spell in modern by a long shot. Path to Exile deals with everything from a troublesome Dark Confidant to big scary eldrazi. It interacts nicely with Leonin Arbiter, forcing your opponents to pay unless they want to have their creature killed by better Swords to Plowshares
Leonin Arbiter-This card is stupid. Leonin Arbiter is good because of the existence of fetches. Ghost Quartering someone with a Leonin Arbiter out is very powerful in modern, as it is a worse Strip Mine, but a Strip Mine none the less. Apart from that, Leonin Arbiter also hits torn pretty hard by shutting down Expedition Map, Sylvan Scrying, and Sanctum of Ugin.
Thalia, Guardian of Thraben is a very powerfully annoying card. While in some matchups she isn't good, she makes up for that by being one of if not your best card. Playing only three of her is, in my opinion, a major pitfall. While she's legendary, she's a must-kill threat against an array of decks. She regularly slows down the opponent by two or three turns, and is poison against storm, and any other combo deck. Needless to say, she's also extremely good against control decks, as they have to kill her before they can kill any of your actual threats.
Tidehollow Sculler-This is my favorite card in all of magic. I love the art, I love the card, and I have a foil playset signed by rk post. Apart from that, Tidehollow Sculler is an amazing piece of disruption. One of the many reasons this card is so good is that it has the old formatting of cards with ETB take something effects. If your opponent kills Tidehollow Sculler in response to its trigger, the leaves the battlefield trigger goes onto the stack on top of its ETB, and resolves first, giving nothing back before taking the card forever. This also is why it's so good in combination with Eldrazi Displacer. If, in response to the ETB trigger, you activate Eldrazi Displacer's ability targeting Tidehollow Sculler, it leaves the battle field, putting the leaves trigger on top of the ETB, but it also puts a new ETB on the stack. You then take a card under Tidehollow Sculler, give the card taken by the original ETB back (it hasn't been taken yet), and then take a card from their hand forever. Perhaps more brutal, is Tidehollow Sculler's interaction with Wasteland Strangler. The interaction is that you take a card with Tidehollow Sculler's ETB, then put it into your opponent's graveyard with Wasteland Strangler's ETB, and kill one of your opponent's creatures.
Wasteland Strangler-This is one of the more expendable cards in the deck, but is still quite good. Apart from the aforementioned interaction with Tidehollow Sculler, other cards that give it food to process are: Path to Exile, Thought-Knot Seer, and sometimes Flickerwisp. Lots of decks also play delve-threats, which can't be killed by Wasteland Strangler, but can still be shrunk by it.
Eldrazi Displacer-This is an absurd card. Its uses with its flicker ability are numerous. most often, it will be used to flicker a blocker or two out of the way, save one of your creatures from a removal spell, or accrue value. Its most notable use is its aforementioned interaction with Tidehollow Sculler, but can also be used to flicker Thought-Knot Seer, or Flickerwisp on the end step to flicker something away until your opponent's end step. Apart from that, it's simply a 3/3 for 3. Also to note, its ability can use Eldrazi Temple eldrazi mana.
Flickerwisp-is the deck's only flying creature. It isn't valuable for that reason alone, but flying is important. Like Eldrazi Displacer, you can flicker a blocker away, save a creature from a removal spell (requires Aether Vial on 3), flicker Thought-Knot Seer, or accrue value from Thraben Inspector, or Blade Splicer. With an Aether Vial on three, Flickerwisp can be played at instant-speed, which means you can vial it in on the end step, causing the exiled card to be gone until your opponent's end step. It can also untap a land.
Silverblade Paladin-Surprisingly, it's actually quite good. In every league I've played with it so far, the paladin has dealt upwards of 8 damage in at least one game. While it is just a beater, the double strike can be very relevant on defense, too. Giving Thought-Knot Seer double strike and swinging for eight is really impressive.
Thought-Knot Seer-It's a 4/4 for 4. It's a hand-attack spell that exiles. It's an eldrazi. It's out of Lightning Bolt range. It has a downside. The downside isn't that bad. It can be flickered with Eldrazi Displacer and Flickerwisp. That's pretty much all I have to say about it.
Next up are the lands.
Basics-I only run three, and have considered, in the past, running 3 plains instead of only two, but I came to the conclusion that, I'm not casting spells through a Blood Moon anyways, and I would rather have an extra Shambling Vent. I'm running a Snow-Covered Plains for the marginal advantage it has against Unmoored Ego, and that it's beautiful.
Shambling Vent-It's very lucky that there's a good creature land in Orzhov colors. The lifelink is often very relevant, but there is some disadvantage that comes with running it and Aether Vial in the same deck. It is, however, almost always better to play out a turn one Aether Vial instead of a turn one Shambling Vent.
Concealed Courtyard-Orzhov fastland.
Caves of Koilos-untapped triland in this deck.
Eldrazi Temple-fuels eldrazi
Ghost Quarter-Don't be afraid to use it against tron if you don't have a Leonin Arbiter.
**Sideboard**
Two Stony Silence-comes in against artifact decks, and completely shuts down most of them. With only two coming in, it isn't worth it to take out Aether Vial, as Stony Silence shuts it down.
Two Orzhov Pontiff-Pontiff is a great card in the sideboard, as it can act as either mass removal, or an anthem. Most often, though, it'll be used as mass removal. The haunt effect is rarely useful, but do keep it in mind. More often, you'll be using Eldrazi Displacer to repeat its effect multiple times in a turn.
Two Fatal Push-Push is one of the premier removal spells in modern, but isn't quite as good as Path to Exile, so I don't run any mainboard. I don't reccomend bringing it in against Hollow One or Grixis Death's Shadow, as it doesn't actually kill their delve threats.
Three Rest in Peace-Bring it in against every graveyard deck in modern. It totally shuts down most decks it's good against unless they have removal for it.
One Blessed Alliance-It's good against burn, Death's Shadow, Slippery Bogle, Infect, and whatever you might need the untap for.
One Bitterblossom-Comes in against every control deck in the format, as it provides incremental value, and against most control decks, the life loss won't matter.
Two Kambal, Consul of Allocation-he's a criminally underrated card in this deck, as he is a must-answer threat against storm and KCI. He also is extremely good against control decks, as he taxes them on every spell they cast.
Two Gideon, Ally of Zendikar-Chad's a large midrange threat that takes over games quickly against control or midrange decks, and is even good against aggro.
