Swamp

Treasury Thrull

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.)
Whenever this creature attacks, you may return target artifact, creature, or enchantment card from your graveyard to your hand.

Thrull Parasite

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.)
{T}, Pay 2 life: Remove a counter from target nonland permanent.

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.)

Vizkopa Confessor

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.)
When this creature enters, pay any amount of life. Target opponent reveals that many cards from their hand. You choose one of them and exile it.

Crypt Ghast

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.)
Whenever you tap a Swamp for mana, add an additional {B}.

Basilica Guards

Defender
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.)

Syndicate Heavy

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.)
At the beginning of each end step, if you gained 4 or more life this turn, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Tithe Drinker

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
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.)

Children of Korlis

Sacrifice this creature: You gain life equal to the life you've lost this turn. (Damage causes loss of life.)

Kingpin's Pet

Flying
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.)

Sorin, Ravenous Neonate

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.)
+2: Create a Food token.
−1: Sorin deals damage equal to the amount of life you gained this turn to any target.
−6: Gain control of target creature. It becomes a Vampire in addition to its other types. Put a lifelink counter on it if you control a white permanent other than that creature or Sorin.

Sorin of House Markov

Lifelink
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.)
At the beginning of each of your postcombat main phases, if you gained 3 or more life this turn, exile Sorin, then return him to the battlefield transformed under his owner's control.

Sorin of House Markov // Sorin, Ravenous Neonate

Knight of Obligation

Vigilance
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.)

Life Insurance

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.)
Whenever a nontoken creature dies, you lose 1 life and create a Treasure token.

Beacon of Immortality

Double target player's life total. Shuffle Beacon of Immortality into its owner's library.

Syndicate Enforcer

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.)

Tainted Sigil

{T}, Sacrifice this artifact: You gain life equal to the total life lost by all players this turn. (Damage causes loss of life.)

Syndic of Tithes

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.

Shard of the Nightbringer

Flying
Drain Life — When this creature enters, if you cast it, target opponent loses half their life, rounded up. You gain life equal to the life lost this way.