doctorhydrogen

Gift of Immortality lets you chuck the same dude over and over.

Angelic Accord usually makes a dude whenever you fling one at someone, giving you another dude to fling at someone which makes you another dude, over and over, etc.

Martyr's Bond punishes everyone else for letting you fling stuff. After all, it's their fault you had to sacrifice a guy to try and kill them, so they may as well be punished for it.

Well of Lost Dreams can draw you a lot of cars in Brion.

Adarkar Valkyrie lets you bring back a guy you just flung, even if it's a guy you stole from someone else.

Greater Good is amazing in Skullbriar. My friend who plays it saccs him to draw a handfull of cards and recast him. It's the best draw spell in his deck, plus it can save you from a Black Sun's Zenith.

Land count tends to be pretty fluid based on a lot of different things for each individual. You don't want to run to0 few obviously, but you don't want to draw eight in a row either, and with 45 you're running a risk of that. Plus if you have a regular playgroup the mulligan rules they use make a difference, as does how much extra draw you have, if you have land filtering/fetch (Land Tax, Tithe) etc. My group lets you take one free partial mulligan, so for me 36 has never been an issue, and some guys I play with run 35 or even 34 in a low cmc deck. I'd say start with 40 maybe to be safe as that's plenty in most situations and adjust downward if you find yourself getting flooded.

You could also broaden your mana base a bit with non-basics. Me personally I'd start with Arcane Sanctum, Command Tower, and Exotic Orchard first as all three are cheap, then Urborg Tomb of Yawgmoth because it does some partial fixing. After that I'd pick up the three shocks as money permits, then the fetches (since they can get your shocks).

For utility lands Academy Ruins would be super useful here.

Also, I consider Chromatic Lantern a must-include in a three-or-more colored deck. It's so, so useful.

Keep an eye on Remand. It's an amazing card in Modern because odds are you're planning on winning next turn, so you don't care if the card you counter goes on top of the person's library where they can draw and play it again. In Commander where the games tend to go longer winning the next turn doesn't happen nearly so often so I think you'll find that delaying some scary spell a turn winds up being much less effective.

Tinker is banned currently.

I also tend to find cards like Waking NIghtmare to be not that effective. Three mana to get a one card advantage isn't nearly s good here as it is in other formats.

With this many artifacts Dispatch is a pretty great targeted removal spell.

If you're curious here's my current version of Sydri: http://www.mtgvault.com/doctorhydrogen/decks/sydri-galvantic-genius-edh-2/

Isn't Demonic Tutor going to be better than Fabricate in every way? I'd run Counterspell over Mana Leak, too.

45 land seems a touch high imo.

Imp's Mischief is great in mono-black especially if you have a commander everyone guns for. There's been so many times I've saved a game by turning a counterspell back on itself or redirecting a removal spell back to the caster, etc. You can even use it to redirect auras onto your dudes. I've stolen a Eldrazi Conscription more than once.

Expedition Map lets you tutor up Cabal Coffers. Caged Sun is probably worth a slot, too. Mana doublers are amazing in mono black.

Since you don't seem to be on too tight of a budget I'd replace Sign in Blood with Necropotence. It's the best draw spell in the format,

Myriad Landscape doesn't really take up a deck slot, and it turns into two swamps.

Spending one mana to cast an artifact that perpetually saves two on every one of your turns is never, ever crap, and I'd wager 99.9% of EDH players share my opinion in that regard. There's a reason it's the most ubiquitous card in the format.

I get not running it for theme reasons, etc. I myself don't run it in my enchantress deck for just that reason. But don't kid yourself regarding how strong it is. It may be literally the best card in EDH.

You are correct, you pick green and that means the blue guy can't counter your stuff, the black guy can't Hero's Downfall, etc. It's really brutal, and almost nobody runs it. Plus it's like a thirty cent card, too.

I'd replace maybe Avatar of the Resolute. You just don't have that much stuff that puts out counters..

Also I'd replace one of the enchant lands with Sakura Tribe Elder, too. Putting a land into play is the same ramp and it's not nearly as vulnerable to removal as an aura and it can't be two-for-oned. Plus it can procc off Lurking Predators and won't screw up Primal Surge. Wood Elves are also decent ramp-on-a-dude, as is Yavimaya Dryad.

Hall of Gemstone does nothing to you, and it makes your spells almost uncounterable and makes multi-colored spells (including commanders) almost uncastable.

Primal Order is going to do a ton of damage to everyone who isn't you.

Myriad Landscape gives you another Krosan Verge.

Skyshoud Claim and Explosive Vegetation both put the lands into play for double landfall triggers.

With that many creatures Lurking Predators would wreck some dudes.

Sol Ring is pretty much NEVER not worth running unless you've got some weird artifact hate thing going on.

In a three color deck I'd run Chromatic Lantern over Mistvein Borderpost all day.

I'd run Hero's Downfall all day over Feast for Blood. Gaining four life is nearly meaningless, and there may be times you need to kill something without having vamps in play. Plus instant speed and having the flexibility to hit Planeswalkers can be invaluable.

Chaos Warp is gonna be your only way to deal with enchantments. Plus it's just a great card. I'd run it in any deck with red.

Wayfarer's Bauble is just a useful card in general, but it can give you one more cheap way to get Cabal Coffers or Urborg, etc.

Triangle of War can often times function as a second Executioner's Capsule.

All those creatures would work amazing with a Lurking Predators.

Depending on how many fliers you go against in your meta Bower Passage would make all your dragons nearly unblockable.

I tried Fauna Shaman but it never did anything. Casting it, waiting a turn, then using it's ability for a creature that I probably couldn't cast right away since I was using mana on a Yisan tutor never once worked out. Gyre Sage that within that same span usually could tap for 4-5 mana was almost always more useful, as was Taiju Preserver against staxx decks or Seeker of the Skybreak to untap Yisan, etc.

Archetype I also ran, but at the 8 drop slot Craterhoof just ended the game, and I never have had a chance to tutor another 8 drop twice in the same game, so he just got in the way.

IMO run more doublers. Odds are you can't afford a Gauntlet of Might, but Gauntlet of Power and Extraplanar Lens are well worth it.

Wayfarer's Bauble gets you an extra land into play easier than Mycosynth Wellspring.

Chaos Warp is gonna be your only way to hit enchantments. I'd run it in any deck running red, it's op as hell.

Twincast being blue seems kinda uncastable here :)

Greater Good is an absolute powerhouse in my friend's 'briar deck. It's useful to have a sacc outlet against Black Sun's Zenith rendering your commander unplayable for the rest of the game, but sometimes when Skullbriar is big it's worth saccing and replaying him just to draw a fistfull of cards, plus he comes back untapped then so he can block next turn.

Since you're running no artifacts why not run something like Creeping Corrosion? Odds are in a multiplayer game it will take out half a dozen mana rocks alone.

Pretty often my friend gets to spend three mana on an Essence Harvest to deal a dozen damage and gain a dozen life. That's a pretty solid value.

Shizo, Death's Storehouse is a good way to get Skullbriar though and there isn't much downside to it. Rogue's Passage is decent, too.

Doubling Season would do good work here, as would Hardened Scales.

Dauthi Embrace is a good way to make Skullbriar unblockable, and unlike an aura it won't get two-for-one'ed.

I think you need a few more bits of removal. Putrefy, Here's Downfall, Beast Within and Maelstrom Pulse are all great.

A board wipe or two wouldn't hurt, either. Black Sun's Zenith isn't a great idea here, and Damnation is expensive, so maybe Decree of Pain?

I think it's really solid. Things I personally would change, keeping budget in mind:

Deglamer or Unravel the Aether over Naturalize: Naturalize won't hit a Theros god or Darksteel Plate or Forge, won't hit a Blightsteel Colossus, etc. Plus it triggers placed-in-the-graveyard effects. Deglamer gets rid of of those problems and avoids most triggers.

Cyclonic Rift is just too good to not run IMO.

Cauldron of Souls is a star in my Jenara version of +1/+1 counters.

Lot of ETB abilities here that would benefit from a Conjurer's Closet