My contribution is Strata Scythe since you seem to have a couple artifacts like it, just so you have a good 3 of to have a better chance of pulling it.

Price of Knowledge

Price of Knowledge is a little bit underwhelming for the mana and i don't think does enough in this deck.

if you want an infinite combo you can play Sanguine Bond and Exquisite Blood

Doubling Cube , Gauntlet of Power , etc. for more mana.

Necropotence is a monoblack must.

Greed , Phyrexian Arena are also needed.

I do like Necropotence , Phyrexian Arena , and Gauntlet of Power . I dont have a spare necro or arena laying around or they would be in but gauntlet I have no excuse. I got it for the deck and have been putting off putting it in. I just dont think Greed is good enough to get a slot when erebos is at the helm and cube I just dont really like.

Oblivion Stone and Nevinyrral's Disk could help you deal with artifacts and enchantments. Xiahou Dun, the One-Eyed could also be of great use for retrieving stuff from your graveyard :)

That name though.

Just for that, +1.

O stone is actually a great idea. I do need to hit some stuff that black cant in its color pie. I'l add it soon.

I really have to suggest Yawgmoth's Will . Bringing back killed creatures is nice, but the real utility is bringing back other hard to bring back spells. If you have a Caged Sun and/or Gauntlet of Power on the field, then things can get crazy. Reanimate is also a nice spell. Have you thought of All Is Dust to get rid of enchantments and Iona, Shield of Emeria ?

Yawgmoth's Will seems great. Although I don't have one so it might be a bit till it makes it in the deck. Reanimate is fine but I dont really want to get to graveyard reliant with this deck and its just a bit underwhelming for a spot in the deck. I do like All Is Dust but I dont have one and if I did there would be another deck it would be going into first. Iona isn't really a factor in my playgroup.

So nobody plays Kaalia of the Vast ? I feel as though you need more early ramp:
Mana Vault
Grim Monolith
Chrome Mox
Mox Diamond
Dark Ritual (getting turn 2 erebos sound nice?)

No kaalia players. People have suggested Dark Ritual before but it just feels like I would want a card with a more long lasting effect then just a one off thing. That being said my curve really doesn't start till 4 and that is a little bit of a problem, so maybe its worth trying. I totally agree with the mana rocks but I don't really like proxying cards and those are pretty darn expensive.

Exsanguinate , Urborg, Tomb of Yawgmoth , Swiftfoot Boots , Lightning Greaves , etc.

No Mercy and Midnight Banshee would be good i think. Also Urborg, Tomb of Yawgmoth for swampwalk on Sheoldred

Given that the whole point of your deck is to blow things up, I think Rise of the Dark Realms will work for you.

In Garruk's Wake over Plague Wind , regeneration is pretty minor and blowing up planeswalkers is big in commander.

I'd suggest putting Geralf's Messenger and Exquisite Blood + Sanguine Bond combo, or at least just Exquisite Blood, because this card is hilarious in EDH.

I really like the direction you're going with this deck! I have an Erebos commander deck and your list is inspiring for mine. In my experience of playing my deck, I think you will be extremely happy with taking out a Swamp for Urborg, Tomb of Yawgmoth The times it will change Boseiju, Who Shelters All, Cabal Coffers, Nykthos, Shrine to Nyx, or Reliquary Tower into a swamp (for Crypt Ghast abuse) are definitely worth the include. Necropotence is busted. Especially in your deck where you are gaining lots of life. Although it's really bad when you're losing so maybe it's not worth the include.

One card not on your maybeboard or in your maindeck that you should strongly consider (in my opinion) is Diabolic Revelation. It's like Sphinx's Revelation for black... o.k. maybe a bit worse... But Being able to draw a whole hand of cards you want late game is insane. Trust me. That's all. Overall, awesome deck.

luke3894 Thanks man, glad I could help . You are totally right with the Urborg, I just don't have a second one laying around or I would just swap it for a swamp right now. I'll have to give Diabolic Revelation a try, I had it in another deck and wasn't a huge fan but that deck didn't ramp as hard as this one so it will probably be better here.

Ghastly Conscription Archfiend of Depravity Buried Alive Victimize Sanguine Bond Exquisite Blood Sorin's Vengeance Palace Siege

You could consider Exquisite Blood and Sanguine Bond unless you're specifically against combos

Underworld Connections?