Exquisite Blood + Sanguine Bond

NyanFries the deck doesn't really need that to win. As awesome as instant win combos are my playgroup doesn't go for ultra cutthroat games.

Why no Karn Liberated or Argentum Armor to deal with things that black can't typically deal with? (like enchantments) You could use Gate to Phyrexia to deal with problem artifacts your opponents have. With the Exquisite Blood + Sanguine Bond combo, those are both just good cards to help offset the life payments for cards, so they have a purpose past an infinite combo and are still worth their slots.

I would recommend cutting Korlash, Heir to Blackblade because he is just a beatstick and doesn't impact the game that much, Baleful Force because your commander is a draw engine so you don't need to jam more into your deck, and past that he is just a beatstick without any abilities. You might want to cut one of your swamp counting artifacts for a mana rock of some kind, Sol Ring or Coalition Relic or something of the like, because your average CMC is pretty high and you only have 35 lands.

as far as your maybe board goes, here are my thoughts:

Caged Sun
Great for ramp, mediocre for buffing your creatures

Crypt of Agadeem
Black has this habit of pulling creatures out of graveyards, so it isn't that great

Dark Prophecy
Run Necropotence instead

Demonic Tutor
Good card. Auto include into any deck that can run it.

Gauntlet of Power
Use Caged Sun over this, but both if you have space

Kokusho, the Evening Star
Unless you are recurring it, this cycle of dragons are typically not worth it

Lake of the Dead
Good card, but you seem to be land light and probably don't want to be sacing lands without a way to recur them like Crucible of Worlds .

Maga, Traitor to Mortals
Just a scalable beatstick, worse than Korlash, so if you are going to use one of them don't use this one.

Magus of the Coffers
Its Cabal Coffers on a stick...why not use it?

Mikaeus, the Unhallowed
In my experience, people look at this for it's No Mercy effect and it gets hated out pretty quick

Necropotence
Use it. The amount of good packed into one card is incredible.

Phyrexian Reclamation
Good one drop, cheap recursion, and you're playing black...paying life is no big deal

Reanimate
"Oh you have an Avacyn in your graveyard? I'll take that now"

Scion of Darkness
Its ability seems pretty awesome, but its very high on the curve. I wouldn't add it in without taking out something else that is that high on the curve

Sorin Markov
Play this if you want people to hate you. It ends games. And friendships.

Toxic Deluge
I honestly think that this is one of the best board wipes in black right now. For three mana, being able to wipe the entire board of everything (including indestructible creatures) is incredibly powerful.

Vampiric Tutor
Use it if you have room, it isn't super important though. I would not use this over Demonic Tutor .

Vampiric Tutor is one of the best cards ever printed. Similarly with Imperial Seal . Tutors should cost as little mana as possible. You have to cast them jsut before your draw step, but still.... they're great.

Korlash is probably going to get the axe and I have been meaning to grab a Necropotence and the tutors I need along with gate to phyrexia. Money's been tight so I've been going off purely trades. I have the crypt of agadeem in there(haven't updated the list yet) and it works, and besides at its worst I can still just tap it for one black. The Maga, traitor to mortals was thought of mainly for his X cost since I can generate a lot of mana.

Black Market !!

Very heavy curve for 34 land. Have you considered Chainer, Dementia Master ? He is amazing.

farKENoath Despite how heavy the curve goes I've never really run into mana issues too much. I have considered him for the deck though.

I second farKENoath's suggestion for more lands, with barely any other acceleration, you should be thinking about 39-40. Trust me, I've built literally hundreds of EDH decks. Also, Exquisite Blood seems good here, it's an unobtrusive card that gets a lot of incidental life gain to offset lifeloss from your general or anything else for that matter, though I could see how your meta could be too competitive for a pure life gain card.

I don't play Edh competitively. Lol so my meta consists of like 5 people including myself. And I too have built a metric fuckton of Edh decks haha. I may tweak the mana base up.

Temporal Extortion is gritty. Baleful Omen will be filthy since you have a ton of high CMC cards... cool deck +1

sorry not Baleful, but Baneful Omen , which has the best flavor text ever.

I used to run Baleful Omen but half the time it would only reveal lands lol so it got cut. I have considered Temporal Extortion though

I would run more lands.. 34 seems sort of low the lowest I'd go is 37 but if you find it works for you than its what ever man! +1!