Circuit Mender

When Circuit Mender enters, you gain 2 life.
When Circuit Mender leaves the battlefield, draw a card.

Getting

Fumulus, the Infestation

Flying, deathtouch
Whenever a player sacrifices a nontoken creature, create a 1/1 black Insect creature token with flying.
Whenever an Insect, Leech, Slug, or Worm you control attacks, defending player loses 1 life and you gain 1 life.

Accursed Marauder

When Accursed Marauder enters, each player sacrifices a nontoken creature of their choice.

Squelching Leeches

Squelching Leeches's power and toughness are each equal to the number of Swamps you control.

Innocent Blood

Each player sacrifices a creature of their choice.

Defiant Bloodlord

Flying
Whenever you gain life, target opponent loses that much life.

Plaguecrafter

When Plaguecrafter enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Felidar Retreat

Landfall — Whenever a land you control enters, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Virus Beetle

When Virus Beetle enters, each opponent discards a card.

Devouring Swarm

Flying
Sacrifice a creature: Devouring Swarm gets +1/+1 until end of turn.

Bringer of the Last Gift

Flying
When Bringer of the Last Gift enters, if you cast it, each player sacrifices all other creatures they control. Then each player returns all creature cards from their graveyard that weren't put there this way to the battlefield.

Huskburster Swarm

This spell costs {1} less to cast for each creature card you own in exile and in your graveyard.
Menace, deathtouch

Ayara, First of Locthwain

Whenever Ayara, First of Locthwain or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Well of Lost Dreams

Whenever you gain life, you may pay {X}, where X is less than or equal to the amount of life you gained. If you do, draw X cards.

Caustic Crawler

Landfall — Whenever a land you control enters, you may have target creature get -1/-1 until end of turn.

Spined Fluke

When Spined Fluke enters, sacrifice a creature.
{B}: Regenerate Spined Fluke.

Leech Gauntlet

Lifelink
Equipped creature has lifelink.
Reconfigure {4} ({4}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Nantuko Husk

Sacrifice a creature: Nantuko Husk gets +2/+2 until end of turn.

Infestation Sage

When this creature dies, create a 1/1 black and green Insect creature token with flying.

Kemba, Kha Enduring

Whenever Kemba, Kha Enduring or another Cat you control enters, attach up to one target Equipment you control to that creature.
Equipped creatures you control get +1/+1.
{3}{W}{W}: Create a 2/2 white Cat creature token.

Vampire Scrivener

Flying
Whenever you gain life during your turn, put a +1/+1 counter on Vampire Scrivener.
Whenever you lose life during your turn, put a +1/+1 counter on Vampire Scrivener.

Go for the Throat

Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature of their choice.

Eaten Alive

As an additional cost to cast this spell, sacrifice a creature or pay {3}{B}.
Exile target creature or planeswalker.

Anowon, the Ruin Sage

At the beginning of your upkeep, each player sacrifices a non-Vampire creature of their choice.

Living Death

Each player exiles all creature cards from their graveyard, then sacrifices all creatures they control, then puts all cards they exiled this way onto the battlefield.

Bilious Skulldweller

Deathtouch
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Nazar, the Velvet Fang

Menace (This creature can't be blocked except by two or more creatures.)
Whenever you gain life, put a feeding counter on Nazar, the Velvet Fang.
Whenever Nazar attacks, you may remove three feeding counters from it. If you do, you draw three cards and you lose 3 life.

Endless Cockroaches

When Endless Cockroaches dies, return it to its owner's hand.

Ashroot Animist

Trample
When this creature attacks, another target creature you control gains trample and gets +X/+X until end of turn, where X is this creature's power.

Wall of Limbs

Defender (This creature can't attack.)
Whenever you gain life, put a +1/+1 counter on Wall of Limbs.
{5}{B}{B}, Sacrifice Wall of Limbs: Target player loses X life, where X is Wall of Limbs's power.

Slimy Dualleech

At the beginning of combat on your turn, target creature you control with power 2 or less gets +1/+0 and gains deathtouch until end of turn.

Swarmyard Massacre

Create two 1/1 green Squirrel creature tokens. Then each creature that isn't an Insect, Rat, Spider, or Squirrel gets -1/-1 until end of turn for each creature you control that's an Insect, Rat, Spider, or Squirrel.

Spinal Centipede

When Spinal Centipede dies, put a +1/+1 counter on target creature you control.

Epicure of Blood

Whenever you gain life, each opponent loses 1 life.

Swarmyard

{T}: Add {C}.
{T}: Regenerate target Insect, Rat, Spider, or Squirrel. (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Corrupted Conviction

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

Nirkana Revenant

Whenever you tap a Swamp for mana, add an additional {B}.
{B}: Nirkana Revenant gets +1/+1 until end of turn.

Wriggling Grub

When Wriggling Grub dies, create two 1/1 black and green Worm creature tokens.

Barter in Blood

Each player sacrifices two creatures of their choice.

Leonin Skyhunter

Vito, Thorn of the Dusk Rose

Whenever you gain life, target opponent loses that much life.
{3}{B}{B}: Creatures you control gain lifelink until end of turn.

Carrion

As an additional cost to cast this spell, sacrifice a creature.
Create X 0/1 black Insect creature tokens, where X is the sacrificed creature's power.

Bloodthirsty Aerialist

Flying
Whenever you gain life, put a +1/+1 counter on Bloodthirsty Aerialist.

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Ebony Fly

Ebony Fly enters tapped.
{T}: Add {C}.
{4}: Roll a d6. Until end of turn, you may have Ebony Fly become an X/X Insect artifact creature with flying, where X is the result.
Whenever Ebony Fly attacks, another target attacking creature gains flying until end of turn.

Enduring Tenacity

Whenever you gain life, target opponent loses that much life.
When Enduring Tenacity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Battlefly Swarm

Flying
{B}: Battlefly Swarm gains deathtouch until end of turn.

Butcher of Malakir

Flying
Whenever Butcher of Malakir or another creature you control dies, each opponent sacrifices a creature of their choice.

Cat Collector

When this creature enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Whenever you gain life for the first time during each of your turns, create a 1/1 white Cat creature token.

Prideful Parent

Vigilance (Attacking doesn't cause this creature to tap.)
When this creature enters, create a 1/1 white Cat creature token.

Call to the Grave

At the beginning of each player's upkeep, that player sacrifices a non-Zombie creature of their choice.
At the beginning of the end step, if no creatures are on the battlefield, sacrifice Call to the Grave.

Dross Hopper

Sacrifice a creature: Dross Hopper gains flying until end of turn.

Arahbo, the First Fang

Other Cats you control get +1/+1.
Whenever Arahbo or another nontoken Cat you control enters, create a 1/1 white Cat creature token.

Swarm of Bloodflies

Flying
Swarm of Bloodflies enters with two +1/+1 counters on it.
Whenever another creature dies, put a +1/+1 counter on Swarm of Bloodflies.

Dawnwing Marshal

Flying
{4}{W}: Creatures you control get +1/+1 until end of turn.

Custodi Lich

When Custodi Lich enters, you become the monarch.
Whenever you become the monarch, target player sacrifices a creature of their choice.

Regal Caracal

Other Cats you control get +1/+1 and have lifelink. (Damage dealt by those creatures also causes you to gain that much life.)
When this creature enters, create two 1/1 white Cat creature tokens with lifelink.

Deadly Grub

Vanishing 3 (This creature enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Deadly Grub dies, if it had no time counters on it, create a 6/1 green Insect creature token with shroud. (It can't be the target of spells or abilities.)

Archfiend of Depravity

Flying
At the beginning of each opponent's end step, that player chooses up to two creatures they control, then sacrifices the rest.

Swamp

Ingenious Leonin

{3}{W}: Put a +1/+1 counter on another target attacking creature you control. If that creature is a Cat, it gains first strike until end of turn. (It deals combat damage before creatures without first strike.)

Bloodbond Vampire

Whenever you gain life, put a +1/+1 counter on Bloodbond Vampire.

Durable Coilbug

{4}{B}: Return Durable Coilbug from your graveyard to your hand.

Abyssal Gatekeeper

When Abyssal Gatekeeper dies, each player sacrifices a creature of their choice.

Dragon Mage

Flying
Whenever this creature deals combat damage to a player, each player discards their hand, then draws seven cards.

Abyssal Gorestalker

When Abyssal Gorestalker enters, each player sacrifices two creatures of their choice.

Demon's Disciple

When Demon's Disciple enters, each player sacrifices a creature or planeswalker of their choice.

Claws Out

This spell costs {1} less to cast for each Cat you control.
Creatures you control get +2/+2 until end of turn.

Merciless Executioner

When Merciless Executioner enters, each player sacrifices a creature of their choice.

Leonin Vanguard

At the beginning of combat on your turn, if you control three or more creatures, this creature gets +1/+1 until end of turn and you gain 1 life.

Blasphemous Edict

You may pay {B} rather than pay this spell's mana cost if there are thirteen or more creatures on the battlefield.
Each player sacrifices thirteen creatures of their choice.

Marauding Blight-Priest

Mortician Beetle

Whenever a player sacrifices a creature, you may put a +1/+1 counter on Mortician Beetle.

Gluttonous Slug

Menace
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Scion of the Swarm

Flying
Whenever you gain life, put a +1/+1 counter on Scion of the Swarm.

Ruthless Winnower

At the beginning of each player's upkeep, that player sacrifices a non-Elf creature of their choice.