MTG Salvation

I've begun playing MTG during the last couple months, and I quickly gravitated towards black's style. This EDH deck has been a work in progress for about a month, and I'd like to read your feedback. I've only played it in 1v1, unsure how it'd perform in a larger multiplayer setting.

OVERVIEW
I've designed this deck to provide an aggressive, controlling, and destructive front. The deck is built to support and build up Ob Nixilis, the Fallen, but can survive without him. Powerful creatures, different flavors of destruction including board wipes, and lots of land cards form the bulk of this deck. Also included is a little bit of tutoring and creature recursion.

COMMANDER
I love Ob Nixilis, the Fallen, because simply by deploying lands I hurt the opponent and make him stronger. If someone takes destroys or takes control of my lands, he grows stronger still as I draw more. I've got 38 lands in my deck for this reason; I've incorporated several lands that will let me draw more lands in the same turn. (Ghost Quarter, Myriad Landscape).

With Burnished Hart + Sheoldred, Whispering One , I can repeatedly pump out lands very quickly. Having Dictate of Erebos on the field makes this action even better.

Tutoring for Sorin Markov and playing his ability to drop the opponent's life down to ten, then simply deploying more lands makes for a fast win.

CONQUER (Creatures)
All of my creatures dual-hat to disrupt my opponent. Prevent life-gain Erebos, God of the Dead Direct damage to player: Pestilence Demon, Gray Merchant of Asphodel, Massacre Wurm. Creature destruction/sacrifice Liliana's Reaver, Grave Titan, Overseer of the Damned, Reaper from the Abyss, Gatekeeper of Malakir, Archfiend of Depravity, Demon of Wailing Agonies. Swamp-heavy deck, so... Squelching Leeches Card Draw Harvester of Souls,Bloodgift Demon

DESTROY (targets, board wipes)
Included are a range of destruction spells. Beginning with cheap and effective targeted assassinations are Tendrils of Corruption, Deathmark, Malicious Affliction, Doom Blade. Next are mid-level creature removals Mutilate, Bile Blight. No black deck is complete without several "nukes" to keep the battlefield in check, especially against token-factories (green, white-red) Nevinyrral's Disk, Extinguish All Hope, In Garruk's Wake. One of my favorite cards against token decks is Sudden Spoiling. It's cheap, and will disable overlapping booster abilities that are so common in elf / sliver decks.

DISRUPT
Mind Rot, Despise, Distress, Thoughtseize can remove key cards and ruin a strategy being formed by the opponent. Exsanguinate Sanguine Bond, Sorin's Vengeance are powerful life removal / life gain cards.

EQUIPMENT
I've tried to keep my equipment cards simple. Trample, lifelink, hexproof were the abilities I was going for, and they usually prove useful on my Commander.

RETURN CREATURES FROM GRAVEYARD
Having these are important to me, since creatures are integral to this deck. Gravepurge + Grimoire of the Dead + Victimize + Quicksilver Amulet

PLANESWALKERS
Liliana of the Veil Liliana Vess Sorin Markov Each of these align with my deck themes: destruction of creatures, direct damage to opponent, tutoring, and creature recursion.

DECK SHORTFALLS
A huge weakness of this deck is enchantment removal, and I know that is a known mono-black issue. Another weakness is a method of repeatedly recovering creatures from the graveyard, for the purpose of sustaining Contamination. Right now, the only repeatable method is Sheoldred, Whispering One.

Some cards you might want to consider adding: Liliana of the Dark Realms; Griselbrand (only for duel/french edh rules); Cabal Coffers; Damnation; Toxic Deluge; Black Sun's Zenith; and Lightning Greaves.

Since it looks like you are running a deck using the multiplayer banlist (Sol-Ring is in your list); you should try to add more sweepers, and some card draw effects like Phyrexian Arena; and Necropotence to boost your chances of seeing more cards in a long multiplayer game. More tutors too like Diabolic Intent; and Grim Tutor, for getting the cards you want to win some games.

These are just suggestions, so just build around Ob-Nixilis some more, and play the heck out of him. Black is a powerful color to be in, and you shouldn't have problems swapping cards in and out of that 99, as there are just too many great cards from black to choose from.

You should run Ghost Town too. It work well with your commander. Some fetch land and a Crucible of Worlds