Pest Summoning

Create two 1/1 black and green Pest creature tokens with "When this token dies, you gain 1 life."

Blight Mound

Attacking Pests you control get +1/+0 and have menace.
Whenever a nontoken creature you control dies, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Overgrown Arch

Defender
{T}: You gain 1 life.
{2}, Sacrifice this creature: Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Nuisance Engine

{2}, {T}: Create a 0/1 colorless Pest artifact creature token.

Infuse with Vitality

Until end of turn, target creature gains deathtouch and "When this creature dies, return it to the battlefield tapped under its owner's control."
You gain 2 life.

Vampiric Rites

{1}{B}, Sacrifice a creature: You gain 1 life and draw a card.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Swamp

Lisette, Dean of the Root

Whenever you gain life, you may pay {1}. If you do, put a +1/+1 counter on each creature you control and those creatures gain trample until end of turn.

Valentin, Dean of the Vein

Menace, lifelink
If a nontoken creature an opponent controls would die, exile it instead. When you do, you may pay {2}. If you do, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Valentin, Dean of the Vein // Lisette, Dean of the Root

Honor Troll

Vigilance
If you would gain life, you gain that much life plus 1 instead.
This creature gets +2/+1 as long as you have 25 or more life.

Restorative Burst

Return up to two target creature, land, and/or planeswalker cards from your graveyard to your hand. Each player gains 4 life. Exile Restorative Burst.

Pestilent Cauldron

{T}, Discard a card: Create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
{1}, {T}: Each opponent mills cards equal to the amount of life you gained this turn.
{4}, {T}: Exile four target cards from a single graveyard. Draw a card.

Pestilent Cauldron // Restorative Burst

Blood Researcher

Menace (This creature can't be blocked except by two or more creatures.)
Whenever you gain life, put a +1/+1 counter on this creature.

Search for Blex

Look at the top five cards of your library. You may put any number of them into your hand and the rest into your graveyard. You lose 3 life for each card you put into your hand this way.

Blex, Vexing Pest

Other Pests, Bats, Insects, Snakes, and Spiders you control get +1/+1.
When Blex dies, you gain 4 life.

Blex, Vexing Pest // Search for Blex

Sapseep Forest

({T}: Add {G}.)
This land enters tapped.
{G}, {T}: You gain 1 life. Activate only if you control two or more green permanents.

Moldervine Reclamation

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

Sedgemoor Witch

Menace
Ward—Pay 3 life. (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays 3 life.)
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Savra, Queen of the Golgari

Whenever you sacrifice a black creature, you may pay 2 life. If you do, each other player sacrifices a creature of their choice.
Whenever you sacrifice a green creature, you may gain 2 life.

High Market

{T}: Add {C}.
{T}, Sacrifice a creature: You gain 1 life.

Claws of Gix

{1}, Sacrifice a permanent: You gain 1 life.

Cram Session

You gain 4 life.
Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Attrition

{B}, Sacrifice a creature: Destroy target nonblack creature.

Golgari Rot Farm

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

Culling Ritual

Destroy each nonland permanent with mana value 2 or less. Add {B} or {G} for each permanent destroyed this way.

Ashnod's Altar

Forest

Grim Backwoods

{T}: Add {C}.
{2}{B}{G}, {T}, Sacrifice a creature: Draw a card.

Pest Infestation

Destroy up to X target artifacts and/or enchantments. Create twice X 1/1 black and green Pest creature tokens with "When this token dies, you gain 1 life."

Hunt for Specimens

Create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Containment Breach

Destroy target artifact or enchantment. If its mana value is 2 or less, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Deadly Brew

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

Chalice of Death

Chalice of Life

{T}: You gain 1 life. Then if you have at least 10 life more than your starting life total, transform this artifact.