Witherbloom Apprentice

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

Dina, Soul Steeper

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

Swamp

Forest

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 creature dies, you gain 1 life."

Pulse of Murasa

Return target creature or land card from a graveyard to its owner's hand. You gain 6 life.

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 Blood Researcher.

Loxodon Warhammer

Equipped creature gets +3/+0 and has trample and lifelink.
Equip {3}

Environmental Sciences

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. You gain 2 life.

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.

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.

Tend the Pests

As an additional cost to cast this spell, sacrifice a creature.
Create X 1/1 black and green Pest creature tokens with "When this creature dies, you gain 1 life," where X is the sacrificed creature's power.

Accomplished Alchemist

{T}: Add one mana of any color.
{T}: Add X mana of any one color, where X is the amount of life you gained this turn.

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.