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.

Radiant Fountain

When Radiant Fountain enters, you gain 2 life.
{T}: Add {C}.

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Witherbloom Apprentice

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

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

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 creature dies, you gain 1 life."

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

Sol Ring

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

High Market

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

Blossoming Bogbeast

Whenever Blossoming Bogbeast attacks, you gain 2 life. Then creatures you control gain trample and get +X/+X until end of turn, where X is the amount of life you gained this turn.

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.

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.

Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.

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.

Command Tower

Exquisite Blood

Whenever an opponent loses life, you gain that much life.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.