Chainer just wants to reanimate dumb stuff. He needs:
- Fatties and creatures with cool ETB triggers
- Ways to get things into graveyards (self-mill, discard, all-mill, entombs)
- Sac outlets to re-reanimate the good stuff and prevent stuff getting exiled
- Lifegain to be able to keep reanimating things
- Backup reanimation for if I can't keep Chainer around

Considerations:
Razaketh - Big boi with a very useful sac outlet, but it's probably a bit too sweaty
Buried Alive - Entomb three dudes with one spell! Just don't know where I put this...
35th land (Command Beacon?)
Exsanguinate - Gain some life so I can keep going
Kokusho - Creature I can use to gain life to keep going, but a bit easy to go off with
Vilis, Broker of Blood - Draw 3 whenever I reanimate something
Blood Artist - Gain some life so I can keep reanimating
Disciple of Griselbrand - Sac outlet that can gain me life if it’s hard to keep using Chainer, but costs 1 mana per sac
Cavalier of Night - Lifelink on a solid body that can also sac something and reanimate something, but I don’t have a ton of 3-drops I need to bring back
Toxic Deluge (previously core) - Cheap sweeper, but Chainer probably doesn't have the luxury of spending life on sweepers
* Meteor Golem - Creature based removal for enchantments and artifacts, but it’s neither exciting or black
Mikaeus the Unhallowed
Priest of Gix - Pays for itself mana wise if I just need something to die, or can gain me mana with a Panharmonicon
Diabolic Intent - Tutor and sac outlet
Mausoleum Secrets - Cheap instant speed tutor that can probably find almost any card in my deck, but I have to reveal it. Also might not turbo mill myself enough for this
Dark Deal - Dump fatties in the yard or dig for lands etc, all while disrupting and possibly dumping others' strong creatures
Swiftfoot Boots (previously core) - More protection for Chainer
* Corpse Connoisseur - Entomb on a recurrable body
Stitcher's Supplier - Cheap self-mill
Shallow Grave - Cheap reanimation at instant speed for a surprise attacker/blocker/ETB trigger, but I don't want to keep track of graveyard order
Twilight's Call, Thrilling Encore - More mass reanimation
Stinging Study - Draw 5 for 5 at instant speed, but it’s not a creature and costs 5 life
Deadly Rollick - Free removal
Mind Stone - Cheap ramp that can cycle later
Carrion Feeder - Free sac outlet that is cheap to play from hand and can be a big beater, but it can’t block and doesn’t have evasion
Sadistic Hypnotist - Both a sac and discard outlet, but only at sorcery speed and on an expensive but bad body
Woe Strider - Free sac outlet that can recur itself and brings along a buddy, but it's not cheap and I don't have much use for a goat
Whisper, Blood Liturgist - Sac outlet and reanimation, but limited and slow
Phyrexian Delver - Being able to get two bodies if I only have mana for one reanimate is nice, but one of the bodies is a vanilla 3/2 and the other one will likely cost a lot of life
Erebos, God of the Dead - Stops lifegain decks, is an indestructible blocker, and can draw cards, but the cost to use him is a bit high
Overseer of the Damned - Big boi with removal that makes incidental bodies for blocking and saccing
Patron of the Vein - Big flier that kills something and continually grows all my vampires
Author of Shadows - Clear opposing yards after I fill them up so they can’t abuse them
Exhume - Cheap reanimation, but too risky?
Bone Shards - Cheap removal that can help me either sac something or discard something
Shriekmaw - Cheap removal that can be reanimated later, but targets are restricted
Fleshbag Marauder, Demon's Disciple, Merciless Executioner - More Fleshbag effects, if I want more
Tevesh Szat - Card draw and sac outlet with a potential win con
Fallen Ideal - Sac outlet that keeps coming back, makes something evasive and possibly lethal if I have enough things to sac
In Garruk's Wake - One-sided sweeper, but it's going to be hard to cast if I don't have a doubler
Callous Bloodmage - Graveyard hate or cantrip
Bontu's Monument - Pseudo ramp that can also gain me some life
Crowded Crypt - Black mana rock that could eventually get me some zombies
Magus of the Coffers - More mana generation
Ghoulcaller Gisa - Get zombies for saccing, but requires tapping
The Golden Throne - Sac outlet that conveniently gets me just the right amount of mana for a Chainer activation, while also providing some protection. Can only be used once per turn though
Attrition - Sac outlet with removal, but it's an enchantment and it costs black mana to use
Dimir House Guard - Free sac outlet that can tutor for something if I don't need it
Undercity Informer - Cheap sac outlet that can mill me
Vampiric Rites - Sac outlet that draws cards and gains a little life, but it's quite expensive to use
Spawning Pit - Free sac outlet, but it can't be reanimated and I don't need the tokens that much
Malicious Affliction - Cheap removal that can get two targets
Skullport Merchant - Sac outlet with a decent reward for saccing, but at a relatively high cost
Bontu the Glorified - Indestructible sac outlet with a high cost to use and minor effect
Gravelighter - Fleshbag effect that can instead be a cantrip. Can be disrupted by others by killing something in response
Dusk Legion Zealot, Skyscanner, Phyrexian Rager - Cantrips that can chump
Biblioplex Assistant - Archaeomancer at home
Azra Smokeshaper - Protect something from destroy-based removal, but doesn't help against exile or bounce
Ravenous Chupacabra, Duplicant - Removal
Balustrade Spy - Potentially big one-shot mill
Necromantic Selection - Sweeper that reanimates something that died
Earsplitting Rats - Everyone discards, then I have a free discard outlet that protects itself
* Crow of Dark Tidings - Cheap flier that mills a little both on entry and on death
Liliana of the Dark Realms - Acquire real estate, screw opposing creatures, increase value of real estate. Might be able to protect her, but is she worth it?
Thorn of the Black Rose - Deathtouching blocker that makes me the monarch
Lampad of Death's Vigil - Sac outlet with some minor life drain, but it's not free
Indulgent Aristocrat - Sac outlet that can make my vampires bigger, but it's pretty expensive to use, and I might not have a lot of vampires
Bloodthrone Vampire - A cheap-to-deploy free sac outlet with little reward
Olivia's Dragoon - Free discard outlet
Erebos’s Emissary - Free discard outlet, but quite expensive to get started, and without a very useful effect
Pack Rat - A discard outlet that can also become threatening, but probably not good enough with more players, more sweepers and higher life totals
Haunted Dead - Discard outlet from the graveyard
Virus Beetle, Liliana's Specter - Make opponents discard cards
Wailing Ghoul - Minor self-mill
Tymaret, Chosen From Death - Targeted grave hate with minor lifegain
Disciple of Phenax - Thoughtseize-effect
Grave Pact - Get some value when I sac my stuff

Consider (might have):
* Legion Vanguard - Cheap sac outlet that can also mill fatties
Dark Privilege - Free sac outlet that can protect Chainer from sweepers
Rotting Rats, Miasmic Mummy - I dump a fatty and everyone else loses a card
Mire Triton - Minor self-mill and life gain on an annoying blocker
Gorging Vulture - Minor self-mill with minor life gain
Plague Mare - Sweeper for x/1s
Bone Shredder - Removal that puts itself back in the yard for re-use, but is limited in what it can kill
Plagued Rusalka - Sac outlet that can shrink stuff, but costs mana to use
Venomous Hierophant - Self-mill and removal/attack deterrent
Skirge Familiar - Get fatties from hand to the yard, and get black mana for Chainer activations by discarding spare cards
Yarok's Fenlurker - Cheap card advantage by getting rid of opposing cards in hand
Bloodflow Connoisseur - Free sac outlet, but unimpressive
Thallid Soothsayer - Sac outlet and card draw, but costs mana to use
Phyrexian Gargantua - Night's Whisper on a 4/4, but without the option of playing it early to find lands
Skemfar Shadowsage - A much fairer Gary. Choose drain or gain, and uses shared creature type instead of devotion. Humans, Vampires, Zombies and maybe Phyrexians should be plentiful, but Chainer makes things into Nightmares
Cabal Initiate - Free discard
Hell Mongrel - Free discard
Moodmark Painter - Make something big and evasive, but it probably still won't connect unless it's already evasive
Vizier of the Scorpion - Get 2 bodies, and make all my zombie tokens have deathtouch
Burglar Rat, Elderfang Disciple - Cheap annoying creatures that can force opponents to discard, but doesn't let me dump something from my own hand
Mesmeric Fiend - Thoughtseize effect
Circuit Mender, Filigree Familiar - Minor lifegain and cantrip
Malakir Blood-Priest - Potentially minor lifegain while also dealing a bit of damage
Reito Sentinel - Minor targeted mill, with some other potential upside
Renegade Reaper, Undead Butler, Eerie Soultender, Necromancer's Assistant - Cheap minor self-mill
Nimana Skydancer - Mess up a scry/tutor to top

Consider (don't have):
* $$ K’rrik - Use more life instead of mana for reanimation and spells
$$ Witch-king of Angmar - Don't hit me, please. Also a discard outlet
$$ Dance of the Dead - Cheap reanimation, and possibly at instant speed. Chainer redundancy
$ Burning-Rune Demon - Tutor two things and get a 6/6 flier
* $ Canoptek Scarab Swarm - Graveyard removal and a real wincon
Tomb Robber - Actually get something from discarding cards, but it costs a mana each
$ Stitch Together - 2 mana reanimation if I can't have Chainer
$$ Vito, Thorn of the Dusk Rose - Give my team lifelink
$ Shadowgrange Archfiend - Removal and lifegain
Blood on the Snow - Sweeper that can also reanimate something
Phyrexian Plaguelord - Free sac outlet that can shrink stuff
Flesh-Eater Imp - Free sac outlet that can just kill someone
Sanguine Spy - Sac outlet that can also mill fatties, and can draw me cards
Primaris Eliminator - Spot removal or sweeper for small dudes
Thought Gorger - A way to dump fatties from my hand without losing cards, or wheeling away dead cards
Nightmare Shepherd - Sac stuff and make a copy if I don't have mana for another reanimate but need another trigger
Liliana's Standard Bearer - Card draw
Spike Cannibal - Counter +1/+1 counter decks by stealing all their counters
Night Clubber - Sweeper for small stuff
Ravenloft Adventurer - Stops other sacrifice strategies, and adds dungeon delving. But it introduces the initiative, which is awkward
Cemetery Desecrator - Planeswalker or creature removal as well as targeted grave hate. Triggers on both ETB and death
Netherborn Phalanx - Tutor up a different 6-drop, then reanimate for burn or raise dead to tutor again
Gravegouger - Graveyard hate (sac in response to first trigger) or save something important from Bojuka Bog
Vampire Hounds, Trespasser il-Vec - Free discard outlet
Chain Devil - 4 mana fleshbag that ensures they can't sac tokens
Torgaar - A way to sac a bunch of stuff so I can reanimate them again, but only on cast. Can also be used to get back to 20 life for more reanimation, or reset someone who gained infinite life
Intellect Devourer - Brain Maggot everyone, except I can use the cards they exile, then sac and reanimate this when I need to refill my options
Tar Fiend - Reanimateable sac outlet that can also empty a hand or dump more fatties in my yard
Mind Maggots - Bin any number of fatties from my hand to make a big dude
Gloomdrifter - Sweeper for small stuff
$ Summoner's Egg - Cheat things from hand into play
$ Erebos, Bleak-Hearted - Big boi that shouldn't be too hard to have active, with a pay-off for saccing things (although costing life) and a way to sac things to remove small things, but with a mana cost
$ Necron Deathmark - Removal and self-mill
$ Canoptek Tomb Sentinel - Permanent removal
$ Tainted Adversary - Can get me extra bodies when cast or reanimated, but they still cost 3 mana per 2 zombies, and they can't block and can only attack once
$ Oona's Prowler - Discard outlet
$$$$$ Phyrexian Dreadnought - Can be reanimated to sac a bunch of creatures
Technomancer - A little self-mill and reanimate some stuff, but requires me to actually have artifact creatures to get
Shadowborn Demon - Removal on a big flier
Clackbridge Troll - Hasty, tramply fatty with political power
Chittering Witch - An expensive sac outlet with a useful effect and supplying a bit of sac fodder
Flesh Carver - Expensive sac outlet that can leave behind a fatty after removal or sac
Triarch Pretorian - Card draw on reanimation
Entomber Exarch - Duress or Raise Dead on a body
Inverter of Truth - "Save" my yard from a Bog effect, or myself from milling out. It does still wipe the yard, though. Worse anti-mill than an eldrazi titan
Eater of Hope - Big flier that can protect itself by saccing things I want to reanimate again, or act as removal
Fell Shepherd - Big guy that lets me sac stuff as removal
Priest of the Blood Rite - Sac fodder that brings along a 5/5 flier that sticks around
Carrion Grub, Flayed One - Minor self-mill
Putrid Imp - Free discard outlet

-----

Considered cuts:
Illuminor Szeras - Tapping to sac is not ideal, even if the sac payoff is sweet
Overwhelming Remorse - While this is going to be cheap removal in most cases, I might not need the extra non-creature based removal
Elder Brain - Gonti on steroids, but needs to attack
Wayfarer's Bauble (core) - Artifact that isn't crucial
Noxious Gearhulk - Creature removal that is also a source of life
Ashnod's Altar - Not sure how much use I'll get out of the colorless mana