doctorhydrogen

At least in my meta Tribute to Hunger wouldn't do much good; there's just too many tokens and mana dorks that can be sacrificed accomplishing nothing. I'd rather run Dreadbore (if you're bargain hunting) or Hero's Downfall. Sever the Bloodline is really underrated, too. Sorc speed sucks, but it can hit indestructible stuff, can be used to wipe multiple tokens at once, wipe out the Avacyn and the one that someone else cloned from it, AND it has flashback. Seriously, it's amazingly versatile and it's never a dead card in hand, and I think Tribute would be. Then again, Tribute is on theme with vampires, and that's pretty cool, too.

Chaos Warp is great if you don't mind spending or trading 15 bucks worth of stuff for one. It's really the only way you can hit enchantments.

It'll only work against a Uril if he/she only has one creature out (and it won't work against Sigarda at all). It just feels like it would be a dead card way more often than it would be an ace in the hole. If you're really teching against an Uril though maybe Council's Judgement? It'll also work against SIgarda, too.

Brave the Sands has the same CMC as Serra's Blessing, and it gives your creatures the ability to block an additional creature as well.

Unmake costs one more than Diabolic edict but it exiles, and you can choose the target.

There are so many anus-wrecking enchantments in EDH I'd find at least one more way to take them out (I'd recommend Return to Dust or Oblation).

Two hidden low cost gems I'd at least consider:

1. Sever the Bloodline. It's an exile effect so it hits Theros gods or Avacyn, it has flashback so you can re-use it, and it lets you take out an army of tokens in one shot.

2. Extinction. It can win games against tribal decks or token decks, and worst case if desperate just name the creature type of a creature you need to have gone and it functions like an expensive Murder. It's won me more game than I can count when someone thinks they're safe behind a wall of elves or tokens or angels or whatever.

Since you're not running any regen effects I'd run Wrath of God over Day of Judgement. Same CMC and Wrath is only a few bucks more.

I'm a big fan of Crackdown in mono-white. There are some decks it completely shuts down.

Scroll Rack is a good card in it's own right, but since you're already running Land Tax it could be amazing.

You for sure want ways to give them trample. Primal Rage, Gruul War Plow and Rancor are good cheap places to start.

Haste is pretty good in a big-ass hydra deck, too. Fervor or Fires of Yavimaya would work.

Worldfire is on the EDH banned list.

I think the only commanders it matters for is Memnarch and Bosh so it's pretty obscure :)

Not true. Activation coast figures into the card's color identity, so Memnarch decks can run blue, Bosh Iron Golem can run red, etc.

Eh, if anything he needs more Blind with Anger-like effects, not less. Stealing a dude, dealing damage with it, gaining that life, and killing it is literally the best thing you can do with Brion. I'm running Blind with Anger, Harness by Force, Mark of Mutiny, Mass Mutiny, Portent of Betrayal, Threaten, Traitorous Blood, Traitorous Instinct, Unwilling Recruit, Act of Aggression, Disharmony, Flash Conscription, Temporary Insanity, Word of Siezing, Zealous Conscripts, Conquering Manticore, Preacher, Jeering Instigator and various ways to recur all of those, and I'd run more if I had room.

As for the rest none seem key, though I do hate to pull Condemn from a deck, just because tucking a General is always good. Oblation probably does that job better though, and it can hit non-attackers and things that aren't creatures.

Malingus is a good dude to throw.

Gift of Immortality will let you chuck the same dude over and over.

Any suggestions will be sub-dollar due to this being a budget deck:

Umake has the same CMC as Murder but it's an exile effect.

Mortify does cost one more mana than Go for the Throat and Doom blade, but it has no restrictions AND it can be used to hit an enchantment. Same for Putrefy but it can hit an artifact.

The new two-colored lands from Khans come into play tapped like Gates but they kick you a life. Since you're not running anything that benefits from Gates they'd seem to be worth swapping in.

Ghost Quarter is a cheap way to deal with someone's troublesome Maze of Ith, Nykthos, etc.

You have Lim Dul's vault in twice. Might be a chance to slot in Plague Wind as another one-sided wipe to kick off Jeleva's ability.

Polymorph might be a good way to turn a used-up Archeomancer or Kaho into another creature. Proteus Staff would do the same but also lets you tuck an enemy commander if need be. Not sure where I'd slot it in though.

Terramorphic Expanse and Evolving Wilds can probably get replaced with fetches now that they're cheap, but I'm guessing you're planning to do that. Exotic Orchard for Transguild Promenade? It's significantly faster and in a three or four player game it's almost always going to provide you all three colors you need.

Yeah, that deck will get you punched in the dick for sure :)

Deglamer or Unravel the Aether over Nature's Claim IMO so you can hit Theros gods or tuck Sharuum or Senn Triplets.

You're gonna have a tough time hitting the threshold on Emeria I think. Run Kor Haven there maybe for one more Maze of Ith effect?

Auramancer's Guise is pretty amazing in Bruna.

Arenson's Aura is very useful. Sac an enchantment, blow up someone else's annoying enchantment, then attack with Bruna and bring the one you sacced right back into play.

I had a real hard time running Krond in my enchantress deck as the commander. That GGGWWW casting cost can be a real bitch to hit even with an ideal mana base, and since he has no innate protection or defense he died pretty fast and took my enchantments with him. Switch to Sigarda (or even Karametra) made life so much easier. I still run him as the commander on occasion instead of just as one of the 99, but it's a massive power drop to do so just because of difficulty in casting. YMMV there, just letting you know my experiences.

Ancestral Mask can be an absolute game-ender in a deck like this.

If you can find a slot, Flickering Ward is really, really useful. The pick-your-protection is always nice to have, but late-game with an enchantress on the field and spare mana you can bounce it over and over as a draw engine or to make angels with Sigil of the Empty Throne.

Nice deck all around :)

Unless you're running some manner of affinity or using some kind of land sacc combo the downside on artifact lands way outweigh the upside. The last thing you need to to lose lands to a Vandalblast, Nev Disk, Austere Command, etc. There's almost no upside short of maybe having a chance to get one or two back after an Armageddon and a ton of downside, or so my experience trying them taught me.

I'd probably run Putrefy over Ultimate Price. Yeah, it costs one more to cast but it doesn't have the "monocolored" distinction and it can hit artifacts if need be.

Farseek won't let you get a forest, which means it's basically 2 mana to get a swamp and put it down tapped. For the same cost Nature's Lore lets you get a forest and put it down untapped which is a better deal IMO. Cultivate and Kodama's Reach cost one more to cast but both let you put any land into play tapped AND let you put a second one in your hand. Value-wise I myself would probably run all three over Farseek, and all are under a quarter to get if you're being budget-minded.

Urborg, Tomb of Yawgmoth is pretty amazing mana fixing in any deck running black.

Maybe find a slot for Glissa the Traitor? Pound for pound she may be the most efficient black/green creature in the game, and she synergizes really well with Ratchet Bomb

With that may planeswalkers the Chain Veil is probably going to be pretty effective.

Killing one player with a single creature seems like a good thing in anyplayer. Your call though :)

Serra Avatar can flat-out end games in a deck with Brion as a commander

Lurking Predators might fit nice here.