Solid list!

That Ophiomancer needs Contamination

Gravestorm potential draw/removal

Arthursb +1

Overall nice deck. You don't have enough lifegain to balance out your lifeloss. You might want to consider adding more to offset it. Perhaps something as simple as a basilisk color?

Imp's Mischief - Speaking of lifeloss, this card is my favorite. Redirect targeted removal, draw and extra turns. Not to mention it can "counter" counterspells. Highly versatile card with the ability to bluff with 2 open mana is strong.

Insidious dreams is one of the worst black tutors and is prime for cutting. You don't get the cards in hand, they are susceptible to mill, and most importantly, discarding cards is additional cost to cast. With all of blacks amazing tutors, this should be swapped IMO.

Given you're basically playing mono black suicide, have you considered Profane Transfusion? It works quite well with your strategy, not to mention great synergy with Necropotence.

Another card that might be worth considering is Rings of Brighthearth. Coffers + Deserted temple + rings + swamps/urborg = infinite black mana. On it's own, it synergizes with your commander, top and villis to draw additional card exchanging mana in place of life. Moreover with top, it allows you to draw based purely on mana. Furthermore, with top and fetchlands you can set up your draws.

What is your answer to artifacts and enchantments? You might want to consider an Oblivion Stone or nev disk. I understand 20% of your deck are enchantments but sometimes the board just needs to go boom. With your commander you should be able to break parity and rebuild more easily.

Another way to potentially answer pesky problems is Worst Fears. It's another pet card of mine but it has huge potential. Make them keep their commander in exile, use their removal on themselves (or another opponent), provide you info of their hand + deck. If its 1v1 after 2 others have died, then you effectively skip their turn by making them tap out and then you can securely go for the win. It's expensive mana wise but it packs quite a punch. The higher cmc also works well with Twilight Prophet

Hello SufferFromEDHD and Profet93, thank you for the comments!

I have tried some of suggested cards, maybe it's worth to share the insights:

• Black has limited lifegain sources that don't depend on sacrifice (eg.: Zulaport Cutthroat), so I compensate it by adding many tutors that search for Gray Merchant of Asphodel. Making Gary the backbone of the deck is, of course, risky;

• Speaking of tutors, Insidious Dreams is horrible for X=1, great for X=2, and usually means "I WIN" for X=3, as it fetches Bolas's Citadel, Sensei's Divining Top and Sheoldred, the Apocalypse, plus acts as a discard outlet when needed;

• I don't focus on sacrifice-based strategies as they naturally decrease devotion, which makes Erebos and Gary less effective. It is also the reason I don't add colorless mass destruction to deal with enchantments: I need my own enchantments to stay;

• Gravestorm is great for devotion and has potential for an extra draw, but it usually backfires, as the opponents remove their best creatures from their graveyard, thus I lose targets for Animate Dead and others;

• I avoid adding combos where the pieces are bad individually. For example, Rings of Brighthearth makes infinite mana, but is a dead card when the other pieces are not already there. Similarly, I have never had success with Contamination in practice;

• Worst Fears is super fun but matchup dependent, I think it's risky to add cards with CMC > 6 that don't 100% help me win the game;

• Profane Transfusion, Mirror Universe, Magus of the Mirror and Soul Conduit are all on my "to test" list, and some "gotcha" cards like Imp's Mischief, Darkness, Sudden Spoiling and Hellish Rebuke too.

Having said all that, in the next update I'll add more creatures and Whip of Erebos in this deck to have more blockers and lifegain. I'm having issues to deal with voltron decks where the commanders reaches high power before I'm able to turn Erebos into a creature.

Solid reasoning. Let me ask you this....

1. How much blue is prevalent in your meta?
2. How often do you cast insidious dreams and then immediately use your commander to put them in your hand? It costs 4 mana to cast, then 6 mana to draw 3 cards + 6 life for a total of 10 mana + 6 life. Would you not be better served by casting Diabolic Revelation for x = 3 for 8 mana to get the cards A) immediately in hand B) Less counterspell downside C) No lifeloss? I understand the discard aspect can be useful, but with all the discard black has, is that aspect of the card worth all of the 3 negatives listed above? I'm aware Sensei's top can dig one card deeper to assist you

To piggyback off of SufferFromEDHD's suggestion, if contamination does not seem to work for you, have you considered Infernal Darkness? It keeps your coffers active, is easy to sustain for 1-2 turns, and acts as counterspell/removal bait.

While not an entirely serious suggestion, have you considered Mind Stone? Only 2 of your artifacts ramp your commander our more quickly. This helps get turn 3 commander. Its ramp when you need it, draw when you don't Solid reliable and dependable.

Deliver Unto Evil - Its recursion and politics (kind of). They either give you back combo piece like citadel or some good reanimation or removal spell. It's cousin, Xiahou Dun, the One-Eyed is an unblockable eternal witness for black cards. Given it's a creature you can recur it to recur important enchantments. Not too bad with Whip of Erebos either

Alhammarret's Archive - I'm sure you've considered it before, is the reason it's not included because its costly and winmore?

About blue:

• Very few blue control players, that's why I avoid the "gotcha" cards. There is a lot of green decks though, so I raised the number of boardwipes.

About Insidious Dreams:

• A huge part of what makes it great is the fact it is an instant. Also, placing cards at the top benefits Bolas's Citadel, which is a win condition.

About Infernal Darkness:

• Last time I tried, I attracted hate from the entire table without advancing my boardstate that much due to the upkeep cost. Sadly, mana rocks circumvent the stax too.

About Alhammarret's Archive:

• Besides being expensive and winmore, it has the potential to be 5 mana "do nothing" card.

About 2 cmc mana rocks:

• Adding some back in the next update. I thought I could simply add more tutors and fetch for big mana, like Nykthos, but it's not working well...

About graveyard recursion:

• Deliver Unto Evil and Xiahou Dun, the One-Eyed are promising! I'll see if they can replace some tutors with them.

Not an entirely serious suggestion but worth considering potentially.....

Dead of Winter - I see you're running snow swamps.

Crystal Chimes - Given 20% of your deck is enchantments, it could help you rebuild after an inevitable wipe.

Cut recommendation - Profane tutor. In the early game its great. Mid game it leaves a lot to be desired. Late game is terrible. I've never had a good experience with that card.

Potential swap - Vampiric Tutor

Victimize - Recursion, works pretty well with Xiahou Dun.