Vicious Rivalry

As an additional cost to cast this spell, pay X life.
Destroy all artifacts and creatures with mana value X or less.

Withering Curse

All creatures get -2/-2 until end of turn.
Infusion — If you gained life this turn, destroy all creatures instead.

Moseo, Vein's New Dean

Flying
When Moseo enters, create a 1/1 black and green Pest creature token with "Whenever this token attacks, you gain 1 life."
Infusion — At the beginning of your end step, if you gained life this turn, return up to one target creature card with mana value X or less from your graveyard to the battlefield, where X is the amount of life you gained this turn.

Turn Stones

For each opponent, you create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Eccentric Pestfinder

Trample
At the beginning of each end step, if you gained life this turn, this creature becomes prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)

Eccentric Pestfinder // Turn Stones

Blech, Loafing Pest

Whenever you gain life, put a +1/+1 counter on each Pest, Bat, Insect, Snake, and Spider you control.

Lumaret's Favor

Infusion — When you cast this spell, copy it if you gained life this turn. You may choose new targets for the copy.
Target creature gets +2/+4 until end of turn.

Grapple with Death

Destroy target artifact or creature. You gain 1 life.

Root Manipulation

Until end of turn, creatures you control get +2/+2 and gain menace and "Whenever this creature attacks, you gain 1 life." (A creature with menace can't be blocked except by two or more creatures.)

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.)

Professor Dellian Fel

+2: You gain 3 life.
0: You draw a card and lose 1 life.
−3: Destroy target creature.
−6: You get an emblem with "Whenever you gain life, target opponent loses that much life."

Bogwater Lumaret

Whenever this creature or another creature you control enters, you gain 1 life.

Defiling Daemogoth

Menace
Whenever a creature you control deals combat damage to a player, you gain 1 life.
At the beginning of your end step, each opponent loses X life, where X is the amount of life you gained this turn.

Stream of Life

Infirmary Healer

This creature enters prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)

Infirmary Healer // Stream of Life

Comforting Counsel

Whenever you gain life, put a growth counter on this enchantment.
As long as there are five or more growth counters on this enchantment, creatures you control get +3/+3.

Follow the Lumarets

Infusion — Look at the top four cards of your library. You may reveal a creature or land card from among them and put it into your hand. If you gained life this turn, you may instead reveal two creature and/or land cards from among them and put them into your hand. Put the rest on the bottom of your library in a random order.

Pest Mascot

Trample
Whenever you gain life, put a +1/+1 counter on this creature.

Reanimate

Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to that card's mana value.

Grave Researcher

At the beginning of your upkeep, surveil 1. Then if there are three or more creature cards in your graveyard, this creature becomes prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)

Grave Researcher // Reanimate

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."

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Stensian Sanguinist

Whenever you attack, target creature gains deathtouch until end of turn. Whenever that creature deals combat damage to a player this combat, this creature becomes prepared. (While it's prepared, you may cast a copy of its spell. Doing so unprepares it.)

Stensian Sanguinist // Exsanguinate

Sylvan Library

At the beginning of your draw step, you may draw two additional cards. If you do, choose two cards in your hand drawn this turn. For each of those cards, pay 4 life or put the card on top of your library.

Ribtruss Roaster

Devour 1 (As this creature enters, you may sacrifice any number of creatures. This creature enters with that many +1/+1 counters on it.)
At the beginning of your end step, create a number of 1/1 black and green Pest creature tokens equal to the number of +1/+1 counters on this creature. They have "When this token dies, you gain 1 life."

Willowdusk, Essence Seer

{1}, {T}: Choose another target creature. Put a number of +1/+1 counters on it equal to the amount of life you gained this turn or the amount of life you lost this turn, whichever is greater. Activate only as a sorcery.