Need:
$$$$ Vampiric Tutor
$$$ Imp's Mischief
$$$$ Necropotence
$ The Black Gate - Unblockability in a land slot
Mithril Coat - Protection

Consider:
* Disturbed Burial - Raise Dead with buyback. Kind of expensive, but if I have mana to cast Phage, I probably have mana for this
* Dark Ritual - Get a faster start or skip ahead a few turns at a crucial point
Rune-Scarred Demon - A tutor that leaves behind a strong body
Gix, Yawgmoth Praetor - Turn my hand of redundant crap into possible wincons from my opponents libraries
Opposition Agent - A way to get more wincons while also preventing others from finding a way to kill me, but at the power level I expect to play Phage there probably aren't that many tutors
Buried Ruin - Get back Torpor Orb or Sundial if they end up in the yard
* Ob Nixilis Reignited - Personal Howling Mine
* Wishclaw Talisman - Cheap tutor
Mask of Griselbrand - Card draw, lifelink, evasion and devotion
* Torment of Hailfire - Game ending mana sink, but not very fun
Oubliette - Removal with devotion
Whip of Erebos - Permanent Phage with Sundial
Deadly Rollick - Free removal, if I can cast Phage. But at that point, I might not need it?
Massacre Wurm - Sweeper for small annoying dudes, and lots of devotion
Viscera Seer - Trigger Endless Whispers, or pair very well with Chainer
Gravelighter
Soul Transfer - Removal and/or raise dead my Phage
Nightmare Shepherd - If Phage dies I can get a backup Phage
Rise of the Dark Realms - Alternative wincon
Diabolic Revelation - Tutor multiple cards when I have tons of mana
Final Parting - Tutor a card to hand, and one to graveyard for when I have something to get it out of there
Syphon Mind - Card draw and disruption
Lashwrithe - A big boy that can make something else big instead
Crux of Fate
In Garruk's Wake, Plague Wind, Deadly Tempest
Ravenous Chupacabra - Removal and devotion
Promise of Power - Card draw with a good rate, but can't be used early
Gilded Lotus
Hedron Archive, Commander's Sphere - Ramp that can draw some cards later
Palace Siege
Hero's Downfall - Might need answers to planeswalkers
Infernal Grasp, Go for the Throat, Dismember - Cheap removal
Price of Fame
Tragic Slip
Malicious Affliction
Leyline of the Void
Liliana the Last Hope - Raise Dead Phage, kill dorks and probably not get a wincon emblem
Sheoldred
Sepulchral Primordial
Greed
Force of Despair - I will probably have a black card in hand to pitch to this
Succumb to temptation, Wretched Confluence - Card draw
Erebos' Intervention - Removal and life gain, or graveyard hate in an emergency
Songs of the Damned
Bontu's Monument - Ramp-esque, with incidental lifegain
Sword of Vengeance - Trample and haste
Nyx Lotus - With 20 creatures I might not have enough consistent devotion
Gonti - Can nab some ramp from a green deck, but not until I already have 4 mana, and risks hitting some big boys I can't cast or stupid elves I don't need. Nice to recur with Chainer, but probably not worth it without a sac outlet

* Maze of Ith - Save Phage from surprise blockers
Homeward Path - Combo with Endless Whispers and sac outlet to kill two people in one turn
Hall of the Bandit Lord - Hasty Phage
Reliquary Tower
Thespian Stage
Terrain Generator, Crypt of Agadeem, Barren Moor
Nykthos - Has potential to produce a lot of mana, but it's probably more likely to simply be a colorless land than it is to net me BB or better

Consider (don't have):
$$$ Deserted Temple - Untap a coffers
Defiler of Flesh - "Ramp" that can also give some evasion
Atrocious Experiment - Another draw 2 lose 2
$ Bubbling Muck - Potentially huge ritual
Gruesome Realization - Draw 2 lose 2, or sweep small dudes
Offer Immortality - Protection
Thrull Wizard - Counter Phage if they kill my safeguard
Ambition's Cost, Ancient Craving - Draw 3 for 4
$$ Sorin the Mirthless - Card draw and bodies, with a sweet ult
Blood on the Snow - Sweeper + reanimation, but cannot be used to reanimate Phage
Dragon Shadow - Always fear for Phage after I get this
Soul Shatter
Geode Golem - Get out Phage without having to pay 7

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Considered cuts:
Sidisi (core) - Not specific to this strategy, and if I don't have bodies to sac this is a very expensive tutor
Drana - Pretty bad if I don't have big mana
Vorpal Sword - Very expensive to use
Key to the City
Baleful Mastery
Fortuitous Find
Grim Discovery
Burnished Hart
Read the Bones, Sign in Blood
Dark Petition

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Cuts:
? Sudden Spoiling - This is basically just a fog or a Trickbind, since I don't have the board presence to make it into a true sweeper
Merciless Executioner, Fleshbag Marauder - Don't want too many of this effect
Unstable Obelisk - 7 mana is just too much
Hagra Mauling - Sidegraded to Curtain's Call
? Chainer - An alternate way to win, but with a dedicated Chainer deck, I probably don't need this in here
Murderous Rider - Removal and devotion, but not very thematic, efficient or impactful
? Erebos - Doesn't really do much in this deck where it's unlikely to be active unless I already have Phage, but if I don't play it here, where will I play it?
Beseech the Queen - I have to reveal what I found, and I can never get something big on-curve
Diabolic Tutor - Upgraded to Demonic
? Infernal Grasp (previously core) - I already have tons of removal
? Bolas's Citadel (previously core) - Probably won't be able to play a lot of relevant spells in a turn with this, and the sac mode probably isn't relevant