Witherbloom Apprentice

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 1 life and you gain 1 life.

Leonin Warleader

Whenever Leonin Warleader attacks, create two 1/1 white Cat creature tokens with lifelink that are tapped and attacking.

Forest

Hateful Eidolon

Lifelink
Whenever an enchanted creature dies, draw a card for each Aura you controlled that was attached to it.

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Dead Weight

Enchant creature
Enchanted creature gets -2/-2.

Plains

Mind Drain

Target opponent discards two cards, mills a card, and loses 1 life. You gain 1 life. (To mill a card, a player puts the top card of their library into their graveyard.)

Feign Death

Until end of turn, target creature gains "When this creature dies, return it to the battlefield tapped under its owner's control with a +1/+1 counter on it."

Vampire Spawn

When this creature enters, each opponent loses 2 life and you gain 2 life.

Call of the Death-Dweller

Return up to two target creature cards with total mana value 3 or less from your graveyard to the battlefield. Put a deathtouch counter on either of them. Then put a menace counter on either of them.

Hallowed Priest

Whenever you gain life, put a +1/+1 counter on Hallowed Priest.

Prosperous Innkeeper

When Prosperous Innkeeper enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Serrated Scorpion

When Serrated Scorpion dies, it deals 2 damage to each opponent and you gain 2 life.

Archfiend's Vessel

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Archfiend's Vessel enters, if it entered from your graveyard or you cast it from your graveyard, exile it. If you do, create a 5/5 black Demon creature token with flying.

Marauding Blight-Priest

Whenever you gain life, each opponent loses 1 life.

Savage Gorger

Flying
At the beginning of your end step, if an opponent lost life this turn, put a +1/+1 counter on Savage Gorger. (Damage causes loss of life.)

Cling to Dust

Exile target card from a graveyard. If it was a creature card, you gain 3 life. Otherwise, you draw a card.
Escape—{3}{B}, Exile five other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)