The goal of this deck is to build up a lot of black devotion in order to either get lots of harpies (Abhorrent Overlord) or lots of damage and life (Gray Merchant of Asphodel).
Removal/Disruption
Doom Blade - Good, cheap removal spell. Gets sideboarded for Dark Betrayal against a mirror.
Hero's Downfall - Gets rid of pesky planeswalkers or can take out a creature if needed.
Drown in Sorrow - Infest 2.0 it's not Mutilate but it does kill quite a few things.
Thoughtseize - This deck doesn't do a lot on turn one so being able to take a look at the opponent's hand and remove a threat is always nice. The 2 life can be regained later when a Gray Merchant of Asphodel hits the table.
Devotion Builders
Pack Rat - The tokens that this card makes also have the mana cost of Pack Rat so you get an extra one devotion. Makes any dead draws into a Pack Rat.
Nightveil Specter - Nice evasive creature for the cost that adds 3 devotion to black or blue and generates card advantage.
Desecration Demon - 6/6 flyer for 4 mana is great and he has a removal spell built in if the opponent decides to sacrifice creatures to him. You can win games from this guy alone if the opponent cannot find an answer to him.
Devotion Outlets
Nykthos, Shrine to Nyx - Can add a metric tonne of mana with just a couple of creatures out on the field. Can also be used to cast blue and red spells using the multi-coloured mana of Nightveil Specter and
Rakdos Shred-Freak
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Gray Merchant of Asphodel - This creature easily hits for 7+ damage when he hits the battlefield. Getting multiple of these out makes things even better. Can be targeted with the Whip of Erebos to trigger his ETB again.
Abhorrent Overlord - The game normally ends when this guy hits the table and brings an army of evasive harpies with him. He is another good target for the Whip of Erebos.
Card Advantage
Liliana of the Dark Realms - Helps to thin your deck by taking swamps out. Can also be used as removal if needed. The '-6' effect is seldom used purely because I never need 4 mana from each swamp when I have the Shrine to Nyx.
Underworld Connections - Generates both devotion and card advantage when it comes into play. Great card for the cost.
Read the Bones - Getting to scry before drawing helps to avoid the dreaded '2 swamps' draw that can sometimes occur. The 2 life loss is measly when a Gray merchant can top you back up.
