Puschkin

While I see the use in Betrothed Fire, you run only a single copy of it and this card is what keeps this deck from being modern legal.

The single Palace Guard also looks random on me, especially since you run only 14 critters, why waste a precious slot on something defensive?

Personally I prefer Figure of destiny over Student of Warfare but it is questionable if either should be used in this since you will be busy with your enchantments. Hopeful Eidolon might be an alternative as well.

Hello, you called me to help on this deck.
Please note that I am very good at tweaking casual and multiplayer decks, especially in keeping the original idea alive and building on it. But although I have lots of tournament exprience, most of that knowledge is outdated since I stopped playing tournament and league games many years ago. This deck seems to be more on the competitive side of things, so take my advice with a grain of salt. I might not be the right authority for this one. But feel free to call me in on other decks.

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Yes, this deck is also singleminded, but in this case that is a good thing - everything else would just make it too slow to work.

You had Chain Lightning in it initially - where is it gone? I think you might have replaced it with Tarfire which is nice with the Ringleader, but remember what you said about Lackey and Insitgator, they are the main threat and it is crucial to remove blockers in order to be able to put the Ringleader into play in the first place. So I think Chain Lightning is better than Tar Fire here, that extra damage might save you the game when the opponent puts out an early toughness-3-blocker.

In the same train of thought you *might* consider Fireblast to kill off a toughness-4-guy and/or a second blocker on turn two or any blocker the same turn you play the Instigator. Yes, it ruins your mana base. But if you have a Lackey/Instigator, you'll cast your stuff for free. Risky move and I don't know what to cut, but I wanted you to consider this option.

In the case Goblin Recruiter turns out to be too slow you might consider Goblin Piledriver.

All of this assumes this is geared for 1-on1 games. If that's not the case, please tell me and I'll start all over ;)

What are Elvish Mystic and Elvish Champion going to do in the sideboard? In what situation would you side them in? These are cards that should be either main deck or not there at all. There should be cards like Elvish Lyrist, Elvish Scrapper, Glissa Sunseeker or, in this case Nullmage Shepard.
Otherwise you'll run into all kinds of problems because this deck is as singleminded as most decks are on MTGVault, the opponent could shut you down with a single card like Teferi's Moat or Ensnaring Bridge and you'll sit there and can do nothing about it. You also don't have another road to victory other than attacking with lots of pedestrians.
I know that you don't want to dillute your maindeck with what-if-scenario-cards but that's why we have sideboards. I bet 13 of your current 15 sideboard cards are just cards that you wanted to have in maindeck but didn't because it was already at 60 cards, so you put them in the side. That's not how sideboards work.

Why not? Cut one or two Curse of Predation for it.

Don't have much time for this, I'll mostly provide deckhalves. Next thing I'll try is to build a control deck and look what a split into two halved will do to it.

All-or-nothing is not my style, so I don't think I can contribute more. Coat of Arms comes into mind, but that is all.

I would run all 4 Utopian Mycon mainboard, no Thallid and two Elvish Farmers in the open slots.

Parallel Lives doesn't really cut the mustard in this deck because it will only produce a 1/1 here and there. I would go with a mix of Thelon Hermit and Thelon of Heavenwood instead.

Generally put, this deck is really singleminded. You have no removal wahtsoever and your sole plan is "generate a mass of saprolings and zerg". Personally I would feel naked with this, especially in multiplayer, but that is maybe also up to taste, because I noticed that most decks here on MTGVault are like this.
Anyway, personally I would add some utility that matches the theme. Stuff like:
Night Soil (if not main, then at the very least in the sideboard!)
Skull Catapult
Sundering Growth
Pendelhaven
Helm of Possession

and for the lategame maybe Monument of Eldrazi (Champion of Lambhold is also good for the endgame but only for the offenive part).

I was going purely by name/style/artwork of the card, not by playablitiy, because you said this is a purely theme deck.

Psychogenic Probe
Crucible of the Worlds
Not of this world (!)
Primal Plasma
Void (look at the picture - a Mech ;) )
Eternal Dominion
World at War
Invasion Plans
Heat Ray (looks like a ship's laser)
Scalpelexis
Graxiplon
Thran Turbine
Worn Powerstone
Enslave
Staff of Domination
Overmaster
(Brutal) Suppression
Teleport
Telekinesis
Telekinetic Bonds
Mind Warp

Oh and I think the Wall of Brambles is the only card that keeps this deck from being Modern legal, so it has definately to go!

Personally I don't see the world in just black & white (or good and evil, that is). Maybe I'll build it soon, would be a hell of a theme deck.

Oh, lol, yeah, that would fit thematically and it has exactly the right casting cost. However, the second Slab you "ripple" into isn't cast, it just triggers the damage of the first one, so it doesn't contribute to storm. If I use the Slab, I will have to do squeeze in the Scroll Racks somewhere.

They are very expensive, you don't want to draw them in your opening hand.

There are a gazillion better options out for both Wall of Brambles and Fog, even when you are on a budget!

Fog:
My personal favourites are Spore Cloud and Respite but I think in this deck you should go with CONSTANT MISTS! Seriously.

Wall of Brambles:
Wall of Blossoms is cheaper and replaces itself.
Wall of Roots or Overgrown Battlement both help you out keeping you alive and provide mana at the same time.
Wolfir Avanger has better stats, has flash and can actually attack.
But given the fact that you are about to drop so many lands you could also consider Grazing Gladeheart, that should also be able to keep you alive.

Maybe replace 4 of the Forests with Treetop Village.

Consider a splash of white for Planar Birth and/or Sacred Ground and/or Terra Eternal.

No, black-blue of course, blue is the colour of mind.

Can't find "Slabs of Death" in any database, what card do you mean?

In that case you'll need tutors even more. Also, I recommend to change some of the creature enchantments to other variants that also grant trample. Armadillo Cloak would be specially useful because it also give lifelink. Right now all you do is making your stuff bigger, but that won't help you anything against regenerators, indestructibles, protection from X and all the other things that you will run into commonly.

Yeah, and I really don't want to see a battle between your shizoid and your paranoid personalities ... hey, I smell a theme-halfdeck right there ;)

You forgot to add cards that allow your walls to actually attack ...
... replace some of the toughness-boosters with cards like Warmonger's Chariot.

Accorder's Shield should probably be Slagwurm Armour.

Since the deck won't do anything without Doran, you might want some tutors or filtering. Eladamri's Call for example?

And I would feel naked without any kind of removal but in the end that's your choice.

I only put the wdm tag there to help your cause and spread the idea, I will change it then.