Grindy if it needs to be, fast if it wants to be.
Introduction
At its core this is a Devoted Druid combo deck. Its primary goal is to untap with Devoted Druid, get a Vizier of Remedies into play to create infinite mana, then cast a lethal Walking Ballista.
The combo has been jammed into the old abzan Collected Company decks to moderate success. It shows up in Elves once in a while, and it also slots adequately into builds of Bant Knightfall. The general consensus, though, is that it is missing something... that the right shell for the combo has not been uncovered yet. This is the right shell, and it is amazing.
What's better than a mana dork for ramping in a creature deck? A hard-to-remove mana dork that makes more than one mana per turn and gives your creatures flash.
Aether Vial might be the best card in the deck. It makes the deck hum. Duskwatch Recruiter
in play with a vial on 2 or 3 is just an unstoppable value engine. Rotating Eternal Witness copies between the battlefield, the graveyard and your hand is unbeatable for a lot of decks. Aether Vial on 2 counters demands respect from the opponent. They cannot tap out against it for fear of losing to instant-speed Devoted Druid. Being able to "flash" in a sideboard creature such as Phyrexian Revoker (in response to, say, a Cranial Plating or a Ugin, the Spirit Dragon) is bonkers. Putting an Eternal Witness into play to get back a card that is targeted by Surgical Extraction is a great feeling.
First and foremost, Eldritch Evolution is a Vizier of Remedies or a Duskwatch Recruiter
if you ever get to untap with Devoted Druid. But it also gives you copies 2 through 5 of Magus of the Moon. It also gets Eternal Witness, Renegade Rallier, or Duskwatch Recruiter
to start grinding your opponent's resources down. Lastly, Eldritch Evolution amplifies all of the sideboard bullets. Having 5 copies of Rhox War Monk against burn for the cost of one sideboard slot is an absolute bargain.
Matchups
Grixis Shadow
The easiest way to win this matchup is off the back of Magus of the Moon, since they usually on play ~two Lightning Bolt and they are NEVER fetching basics. Your "backup" plan is to grind them out. They have so many 1-for-1s, if you can get in two or three 2-for-1s you probably win. Kolaghan's Command is one of the scariest cards from them, because it is a real 2-for-1. Snapcaster doesn't count, because the body rarely matters. The other N-for-1 they can start cashing out on is chump blocks forced by Death's Shadow beats. You can assemble a chain of Eternal Witness copies to address this if needed. Use Devoted Druid as removal bait. Your real plan is to use Duskwatch Recruiter
and Renegade Rallier to run them out of removal, and then combo-kill (assuming Magus of the Moon didn't already steal the game). If you're on the draw and they didn't do something on turn 1, lead with a mana dork before Aether Vial because Vial is a very important card in the matchup and you don't want it to get hit by a Stubborn Denial.
Sideboard plan IN: Fairgrounds Warden, Sigarda, Host of Herons. OUT: 1x Vizier of Remedies, 1x Noble Hierarch. You might also consider Burrenton Forge-Tender if you're worried about Kozilek's Return or (less typical nowadays) Anger of the Gods. In this matchup, getting a Sigarda, Host of Herons into play is near impossible for them to beat. She is typically a two-turn clock, and they don't have the mana and time to clear your chump blockers to get a lethal Death's Shadow through.
Affinity
Game 1 usually favors you, but if they have Cranial Plating and Galvanic Blast in their opener it can get scrappy. You're just racing to the combo. This is one of the few matchups you may want to lead with mana dork before Aether Vial if turn 2 Eldritch Evolution is the fastest way to get to Devoted Druid.
Sideboard plan IN: card:Caustic Caterpiller, Kataki, War's Wage, 2x Phyrexian Revoker, Reclamation Sage. OUT: 2x Collected Company, Magus of the Moon, 1x Renegade Rallier, 1x Eternal Witness. You may consider bringing in Burrenton Forge-Tender over one of the remaining Eternal Witness but my preference is to play around Whipflare more proactively. You might also consider Linvala, Keeper of Silence if you're on the play, because shutting down Arcbound Ravager and Steel Overseer while locking up the air is nice. Some important interactions, post-board: Whipflare does not kill Phyrexian Revoker. Vizier of Remedies stops Inkmoth Nexus from killing your Birds of Paradise. card:Caustic Caterpiller is often better to get with Chord of Calling than Reclamation Sage because it works better with Eternal Witness and Renegade Rallier.
Eldrazi Tron
This might be the only matchup that is sub-50% but it is still very winnable. Magus of the Moon isn't as good as it seems like it should be. It can slow them down, but it won't usually take them off colorless mana between card:Mindstone and Expedition Map for Wastes. Pursue the combo as aggressively as you can. The most typical way for them to win is to get to an early All Is Dust or natural tron into Walking Ballista to keep you off your combo and value engines. Chalice of the Void has a hard time hosing you because of Aether Vial.
Sideboard plan IN: Caustic Caterpillar, Fairgrounds Warden, Gaddock Teeg, 2x Phyrexian Revoker, Sigarda, Host of Herons. OUT: 2x Collected Company, Magus of the Moon, 2x Eternal Witness, 1x Renegade Rallier. Sigarda, Host of Herons turns off All Is Dust and is a big body. It is worth noting that Aether Vial does not die to All Is Dust or Ugin, the Spirit Dragon so you can always threaten an end-of-turn Devoted Druid through either of those.
Burn
This is a pretty even matchup, if they figure out they are supposed to play the role of control. The mana base in this deck lets you preserve your life total pretty well, between the three basic Forests and the 3 copies of Razorverge Thicket. If they don't have 2 Searing Blaze or one copy plus a Grim Lavamancer you're in good shape.
Sideboard plan IN: Burrenton Forge-Tender, Dryad Militant, Fairgrounds Warden, Kitchen Finks, Reclamation Sage, Rhox War Monk. OUT: 2x Collected Company, 1x Renegade Rallier, 2x Eternal Witness, Magus of the Moon. The Dryad Militant is just a cheap guy that can trade with a Goblin Guide or devalue Grim Lavamancer a bit. Nothing great, but it helps tighten up the curve. Post-board, if they don't have mana for Skullcrack or Atarka's Command typically get Kitchen Finks before Rhox War Monk. The Reclamation Sage can kill an Eidolon of the Great Revel, and trade or chump in combat. Post-board they will usually have 3-4 copies of Path to Exile. One of the hardest decisions you will make with this deck is whether you should activate Devoted Druid twice to put it in the graveyard in response to Path to Exile in various matchups. It is very situation-dependent, so just keep in mind that even if you think the answer is obvious, give it an extra thirty seconds of thought and try to look ahead several turns.
Dredge
There is exactly one card that matters in this matchup, and it is called Conflagrate. If they hit one copy of it, the game is roughly a coin flip. If they hit two copies of it, you are losing (ok I have one great story to tell about an exception to this, in round 9 of Grand Prix Las Vegas... but I'll save that for a different day). Race your way to the combo, use Aether Vial as an instant-speed threat to either put in Devoted Druid after their Conflagrate or get it up to 3 so you can put in Renegade Rallier to resurrect your Devoted Druid that bit the dust.
Sideboard plan IN: Burrenton Forge-Tender, Dryad Militant, Gaddock Teeg. OUT: 2x Collected Company, Magus of the Moon. You might notice something about the 3 cards that come in... they are all to deal with Conflagrate. Their post-board Collective Brutality can be rough but you still have the full value engine in the deck. Gaddock Teeg also shuts down Engineered Explosives out of the board which is nice. Darkblast is a nuisance but not back-breaking by any means.
UW Control
This is a dream matchup. 80+ percent, easily, as long as you know how to play it. I have had opponents resolve 3 and even 4 copies of Ancestral Vision and still be behind in cards. Devoted Druid serves as a good magnet for early removal. Remember to think carefully about whether you'd rather have Devoted Druid in the graveyard as opposed to letting it exile and getting a basic Forest of Path to Exile. Your main plan here is to use Aether Vial and the value creatures to grind their permission and removal down to nothing. It will usually take a long time, but it will happen. Sometimes Magus of the Moon takes a game (or two) off them.
Sideboard plan IN: Eidolon of Rhetoric, Gaddock Teeg, Kitchen Finks. OUT: 2x Collected Company, 1x Noble Hierarch. It seems counter-intuitive to take out Collected Company when it's such a great card to resolve against control. However, you're usually on the draw in game 2 (I'm dead serious about game 1 being pushover) and they have Dispel out of the board. Taking out Collected Company is also a good idea when you plan to get Gaddock Teeg into play on turn 3 or 4 a majority of the time, to shut down planeswalkers and board-sweepers. Shaving one mana dork is just an acknowledgement of the sweepers they plan to use against you. It's better to keep Birds of Paradise because hard-casting a naturally drawn Magus of the Moon is quite nice on turn 2.
Matchup XYZ that I haven't covered yet
Patience. I may or may not get to it.
Ok let's talk about that Fauna Shaman
I admit it gets targeted down a lot, before it gets to activate. When it does activate, it's at instant speed and with an Aether Vial in play that feels really good, both pre- and post-board. It also further amplifies sideboard choices. Also, if it's getting targeted down... great! It's a very good card to get back with Renegade Rallier on turn 3 (turned on by fetch land of course), and if they are playing into a 1-for-1 game plan, you have them right where you want them.
