Pontiff of Blight

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Other creatures you control have extort. (If a creature has multiple instances of extort, each triggers separately.)

Authority of the Consuls

Creatures your opponents control enter tapped.
Whenever a creature an opponent controls enters, you gain 1 life.

Suture Priest

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.

Exquisite Blood

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

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Exsanguinate

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

Soul Warden

Whenever another creature enters, you gain 1 life.

Blind Obedience

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Artifacts and creatures your opponents control enter tapped.

Blood Artist

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

Tablet of the Guilds

As this artifact enters, choose two colors.
Whenever you cast a spell, if it's at least one of the chosen colors, you gain 1 life for each of the chosen colors it is.

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on this enchantment. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if this enchantment has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

Sunscorch Regent

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on this creature and you gain 1 life.

Serra Ascendant

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
As long as you have 30 or more life, this creature gets +5/+5 and has flying.

Debt to the Deathless

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

Auriok Champion

Protection from black and from red
Whenever another creature enters, you may gain 1 life.