I thought I'd share my Kuro deck I've been playing with lately. The plan is to gain enough life and ramp up to enough mana to take advantage of Kuro. The deck has other things to do with the life, such as drawing cards, and it can also tutor and kill creatures (mono-black specialties). The deck is rounded off by vampire and demon tribal sub-themes.
Horobi is symmetric, but then so is Damnation. Getting both Kuro and Horobi to stick could give you control of the board, at least for a little while.
Another suggestion: Drana, Kalastria Bloodchief instead of Stronghold Overseer. Drana is quite a bit stronger, as she is removal instead of a quasi-fog effect, but you'd be swapping a demon for a vampire, if that matters flavor-wise (I do have a Drana, if you need one :D)
...not only is the total number of players expanding very quickly, but at the same time a greater and greater number of those players are being pushed to only desire a small subset of the available cards. These combined forces drastically increase demand for those cards and cause the values of just those specific cards to often balloon out of proportion.