Ramp:
Gyre Sage: Mana Dork
Solemn Simulacrum: (R) Basic to play tapped. Repeatable with Glissa
Sol Ring: Mana Rock
Fixing/Consistency:
Expedition Map: (R) Any land to hand. Repeatable with Glissa
Other: 
Jet Medallion: Black spells cost 1 less
Sword of Feast and Famine: Untaps all lands

Kamahl, Fist of Krosa is just mean in this deck... But consider it.. just in case.

Notable possibilities from Sideboard:
Dusk Urchins: possible 3 cards drawn on death (normal). At least 1 draw. (Could be more with pump)
Deity of Scars:  is a large regenerate creature with upside from -1/-1

Notes:
1. Only 1 infect creature. Not likely to cause problem
2. Consider static pump effects for creatures that intentionally carry -1/-1 counters
3. Deck probably needs some land ramp or consistency spells
4. Needs early game creatures added. Ramp maybe?

Strengths:
1. Opponents creatures get weaker and weaker.
2. Proliferate gets through hexproof and shroud
3. Proliferate will boost Planeswalkers
4. Glissa supports proliferate
5. Vhati il-dal supports killing things
6. Gain control of opponents creatures with -1/-1 counters
7. Use Wickerbough Elder or Grim Poppet with Torture to destroy things
8. Use Quillspike to remove -1/-1 counters from own creatures to pump quill spike

Weaknesses:
1. Low life gain
2. Few draw sources
3: Low creature count
4. Few wipes
5. May have difficulty with fast decks
6. May have difficulty with +1/+1 decks:
7. May have difficulty with Flying + Hexproof creatures
8. Weak commanders for theme
9. -1/-1 may hurt self as well
10. Little ramp
11. Deck's creatures that hold -1/-1 to do effects are fragile
12. Little recursion

Tokens: 
Flourshing Defenses: gain a 1/1 elf for each -1/-1 given

Tutor:
Demonic Tutor: Sorcery - To hand 
Vampiric Tutor: Instant - To top of deck

Life Gain:
Garruk Apex Pred: Gain life when destroying a creature

Proliferate:
Core Prowler: (R) proliferate on death. Repeat with Glissa
Plaguemaw Beast: (R) Sac a critter and tap to proliferate
Grim Affliction: Spell, Proliferate on cast
Throne of Geth: (R) Sac an artifact to proliferate, Repeatable with Glissa
Contagion Clasp: (R) pay and tap to proliferate
Contagion Engine: (R) pay and tap to proliferate twice

Draw: 
Ob Nix Reignited: (R) +1: Draw a card, lose 1 life
Phyrexian Arena: (R) Draw a card, lose 1 life
Deathreap Ritual: (R) Draw 1 card at the end of a turn where a creature died
Read the bones: Scry 2, Draw 2, Lose 2 life
Solemn Simalcrum: (R) Draw one on death. Repeatable with Glissa
Nihil Spell Bomb: (R) Draw one when going to grave. Repeatable with Glissa.

Wipes:
Black Sun's Zenith: (R) Creatures
Pernicious Deed: Creatures, Artifacts, Enchantments

Removal:
(R) Repeatable
Permanent: 
Beast Within: Gives player a 3/3 beast instead
Maelstrom Pulse: Destroy all tokens/cards on board with same name as target
Song of the Dryads: target becomes forest
Non-land Permanent: 
Vraska: (R) Destoy target on -3
Abrupt Decay: Destory target with cmc 3 or less
Non-Creature Permanent: 
Woodfall Primus: (R?) On ETB, destroy. Persist
Land: 
Creature: 
Glissa: (R), Deathtouch, First Strike
Sourceress Queen: (R) target becomes a 0/2
Reaper of the Wilds: (R?) Deathtouch
Skinrender: 3 -1-1 counters
Vhati il-dal: (R) target power or toughness becomes 1
Grim Poppet: remove self -1-1 to give target -1-1 counter. starts with 3 counters
Dismember: Target gets -5/-5 until end of turn
Hero's Downfall: Destroy target
Putrefy: Destroy target
Sudden Spoiling: target players creatures become 0/2
Black Sun's Zenith: (R) X -1/-1 counters
Incremental Blight: 1 target gets 1 counter, 1 gets 2, 1 gets 3
Crumbling Ashes: (R) per controller's upkeep, kill a creature with a -1/-1
Ob Nix: (R) Destroy target on -3
Garruk, Apex Pred: (R) Destroy target on -3
Executioner's Capsule: (R) Destroy Target. Repeatable with Glissa.
Artifact: 
Wickerbough Elder: (R?) remove a -1-1 on self to destroy, starts with 1
Putrefy: Destroy target
Sylvok Replica: (R) Destroy target. Repeatable with Glissa.
Enchantment: 
Wickerbough Elder: (R?) remove a -1-1 on self to destroy, starts with 1
Sylvok Replica: (R) Destroy target. Repeatable with Glissa.
Planeswalker: 
Hero's Downfall: Destroy target
Garruk, Apex Pred: Destroy Target on +1

Analysis:
-1/-1 sources
Repeatable:
Corrosive Mentor: All black creatures have wither
Necroskitter: Wither
Core Prowler: Infect
Harbinger of Night: -1/-1 for each creature per controller's upkeep
Lockjaw Snapper: Wither
Noxious Hatchling: Wither
Carnifex Demon: ability to add -1/-1 to each creature by removing a -1/-1 from itself. Starts with 2 counters.
Midnight Banshee: Wither. -1/-1 for each nonblack creature during controller's upkeep
Grim Popper: can remove a -1/-1 from self to give to target. Starts with 3 counters.
Black Sun's Zenith: x -1/-1 to all creatures, shuffle into deck.
Blowfly Infestation: Enchantment, whenever a creature with a counter dies, put a counter on target


Non-Repeatable:
Skinrender: 3 -1/-1 counters to target on ETB
Soul Snuffers: -1/-1 to each creature on ETB
Grim Affliction: Spell, target gets -1/-1 counter
Incremental Blight: Spell, 1 target gets 1 counter, 1 gets 2 counters, 1 gets 3 counters.
Contagion Clasp: Artifact, on ETB target gets 1 counter
Contagion Engine: Artifact, on ETB each creature gets 1 counter
Torture: Enchantment, ability to add 1 counter to enchanted creature

Drana from BFZ is a consideration

Ob Nixils Reignited from BFZ will be added (Replacing Ob Nix of the black oath)