Necrosynthesis

Enchant creature
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature."
When enchanted creature dies, look at the top X cards of your library, where X is its power. Put one of those cards into your hand and the rest on the bottom of your library in a random order.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Astarion's Thirst

Exile target creature. Put X +1/+1 counters on a commander creature you control, where X is the power of the creature exiled this way.

Ancient Animus

Put a +1/+1 counter on target creature you control if it's legendary. Then it fights target creature an opponent controls. (Each deals damage equal to its power to the other.)

Deadly Brew

Each player sacrifices a creature or planeswalker. If you sacrificed a permanent this way, you may return another permanent card from your graveyard to your hand.

Persistent Specimen

{2}{B}: Return Persistent Specimen from your graveyard to the battlefield tapped.

Colossal Majesty

At the beginning of your upkeep, if you control a creature with power 4 or greater, draw a card.

Fireshrieker

Equipped creature has double strike. (It deals both first-strike and regular combat damage.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Deathsprout

Destroy target creature. Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Bloodsoaked Champion

Bloodsoaked Champion can't block.
Raid — {1}{B}: Return Bloodsoaked Champion from your graveyard to the battlefield. Activate only if you attacked this turn.

Prodigious Growth

Enchant creature
Enchanted creature gets +7/+7 and has trample.

Scepter of Celebration

Equipped creature gets +2/+0 and has trample.
Whenever equipped creature deals combat damage to a player, create that many 1/1 green and white Citizen creature tokens.
Equip {3}

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Raised by Giants

Commander creatures you own have base power and toughness 10/10 and are Giants in addition to their other types.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Swamp

Wilson, Refined Grizzly

This spell can't be countered.
Vigilance, reach, trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Choose a Background (You can have a Background as a second commander.)

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Finality

You may put two +1/+1 counters on a creature you control. Then all creatures get -4/-4 until end of turn.

Find

Return up to two target creature cards from your graveyard to your hand.

Find // Finality

Vindictive Vampire

Whenever another creature you control dies, Vindictive Vampire deals 1 damage to each opponent and you gain 1 life.

Mitotic Slime

When Mitotic Slime dies, create two 2/2 green Ooze creature tokens. They have "When this creature dies, create two 1/1 green Ooze creature tokens."

Boar Umbra

Enchant creature
Enchanted creature gets +3/+3.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Explorer's Scope

Whenever equipped creature attacks, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Golgari Rot Farm

Golgari Rot Farm enters tapped.
When Golgari Rot Farm enters, return a land you control to its owner's hand.
{T}: Add {B}{G}.

Grim Haruspex

Morph {B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
Whenever another nontoken creature you control dies, draw a card.

Moldervine Reclamation

Whenever a creature you control dies, you gain 1 life and draw a card.

Zulaport Cutthroat

Whenever Zulaport Cutthroat or another creature you control dies, each opponent loses 1 life and you gain 1 life.

Reassembling Skeleton

{1}{B}: Return Reassembling Skeleton from your graveyard to the battlefield tapped.

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Naturalize

Golgari Germination

Whenever a nontoken creature you control dies, create a 1/1 green Saproling creature token.

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Ordeal of Nylea

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Nylea.
When you sacrifice Ordeal of Nylea, search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Tainted Wood

{T}: Add {C}.
{T}: Add {B} or {G}. Activate only if you control a Swamp.

Soul's Majesty

Draw cards equal to the power of target creature you control.

Awakening Zone

At the beginning of your upkeep, you may create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this creature: Add {C}."

Cloakwood Hermit

Commander creatures you own have "At the beginning of your end step, if a creature card was put into your graveyard from anywhere this turn, create two tapped 1/1 green Squirrel creature tokens."

Nemata, Primeval Warden

Reach
If a creature an opponent controls would die, exile it instead. When you do, create a 1/1 green Saproling creature token.
{G}, Sacrifice a Saproling: Nemata, Primeval Warden gets +2/+2 until end of turn.
{1}{B}, Sacrifice two Saprolings: Draw a card.

Explore

You may play an additional land this turn.
Draw a card.

Nested Shambler

When Nested Shambler dies, create X tapped 1/1 green Squirrel creature tokens, where X is Nested Shambler's power.

Verdant Embrace

Enchant creature
Enchanted creature gets +3/+3 and has "At the beginning of each upkeep, create a 1/1 green Saproling creature token."

Wild Growth

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.

Regrowth

Return target card from your graveyard to your hand.

Thran Power Suit

Equipped creature gets +1/+1 for each Aura and Equipment attached to it and has ward {2}. (Whenever equipped creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Hunter's Prowess

Until end of turn, target creature gets +3/+3 and gains trample and "Whenever this creature deals combat damage to a player, draw that many cards."

Corrupted Conviction

Creakwood Liege

Other black creatures you control get +1/+1.
Other green creatures you control get +1/+1.
At the beginning of your upkeep, you may create a 1/1 black and green Worm creature token.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Cultist of the Absolute

Commander creatures you own get +3/+3 and have flying, deathtouch, "Ward—Pay 3 life," and "At the beginning of your upkeep, sacrifice a creature."

Grismold, the Dreadsower

Trample
At the beginning of your end step, each player creates a 1/1 green Plant creature token.
Whenever a creature token dies, put a +1/+1 counter on Grismold, the Dreadsower.

Midnight Reaper

Whenever a nontoken creature you control dies, Midnight Reaper deals 1 damage to you and you draw a card.

Hydra's Growth

Enchant creature
When Hydra's Growth enters, put a +1/+1 counter on enchanted creature.
At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.

Snake Umbra

Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals damage to an opponent, you may draw a card."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Jungle Hollow

Jungle Hollow enters tapped.
When Jungle Hollow enters, you gain 1 life.
{T}: Add {B} or {G}.

Ram Through

Target creature you control deals damage equal to its power to target creature you don't control. If the creature you control has trample, excess damage is dealt to that creature's controller instead.

Bind Spirit

Return target creature card from your graveyard to your hand. (Then exile this card. You may cast the artifact later from exile.)

Ghost Lantern

Whenever a creature you control dies, put a +1/+1 counter on equipped creature.
Equip {1}

Ghost Lantern // Bind Spirit

Mask of Memory

Whenever equipped creature deals combat damage to a player, you may draw two cards. If you do, discard a card.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Necroblossom Snarl

As Necroblossom Snarl enters, you may reveal a Swamp or Forest card from your hand. If you don't, Necroblossom Snarl enters tapped.
{T}: Add {B} or {G}.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Bojuka Bog

Bojuka Bog enters tapped.
When Bojuka Bog enters, exile target player's graveyard.
{T}: Add {B}.

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

Viridian Emissary

When Viridian Emissary dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Blackblade Reforged

Equipped creature gets +1/+1 for each land you control.
Equip legendary creature {3}
Equip {7}

Temple of Malady

Temple of Malady enters tapped.
When Temple of Malady enters, scry 1.
{T}: Add {B} or {G}.

Colossification

Enchant creature
When Colossification enters, tap enchanted creature.
Enchanted creature gets +20/+20.

Rogue's Gloves

Whenever equipped creature deals combat damage to a player, you may draw a card.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Tyrite Sanctum

{T}: Add {C}.
{2}, {T}: Target legendary creature becomes a God in addition to its other types. Put a +1/+1 counter on it.
{4}, {T}, Sacrifice Tyrite Sanctum: Put an indestructible counter on target God.

Read the Bones

Scry 2, then draw two cards. You lose 2 life. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Poison-Tip Archer

Reach (This creature can block creatures with flying.)
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Whenever another creature dies, each opponent loses 1 life.

Eternal Thirst

Enchant creature
Enchanted creature has lifelink and "Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature." (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)