Great deck! Nice idea!

I would try to replace Liliana Vess with Liliana of the Veil.

Would replace Black Sun's Zenith with Damnation.Add Nykthos, Shrine to Nyx and replace Lashwrithe with Profane Command for sinking the mana generated.

Maybe add in Urborg, Tomb of Yawgmoth since it makes you lands swamps in addition to there other types. So your Swamps would be "Basic land - Swamp, Swamp". It will make Korlash, Heir to Blackblade have twice as much power and toughness. Another good card would be Cabal Coffers which also works with Urborg. Another card that synergizes with Urborg is Lashwrithe, which is already in the deck.

What set is korlash, heir to the blackblade

futuresight.

Firebirddy i believe you are incorrect with urborg creating a double swamp for two counts per swamp on lashwrithe, a swamp cannot become a swamp if it is already, however it will make the nythkos a swamp

Psyrup42, I just checked the ruling and you are correct. Ignore my previous comment.

You should add a few Nykthos, Shrine to Nyx since you've got creatures that cost double black, triple black and even quadruple black and that can end up being some great mana ramp.

Cut 3x Shriekmaw and 1 Disfigure for 4x Liliana of the Veil. Don't cut Phyrexian Arena for anything except more card draw. Dark Confidant or Sword of Fire and Ice.

If you don't own Damnations already then maybe start with one and 2x Drown in Sorrow.

How about 3x Ghost Quarter and 1x Urborg, Tomb of Yawgmoth. It'll help your Tron match up.

How about 2x Gurmag Angler or Tombstalker? Gotta use your grave for something.

I'd say liliana over arena all day. She wins games on her own, and has far greater utility than arena. +1

Mutilate is almost a better Damnation in mono black decks (better in that it gets around indestructible) plus it's like fifty cents so that helps.