Marsh Flats

{T}, Pay 1 life, Sacrifice Marsh Flats: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Sovereign's Bite

Target player loses 3 life and you gain 3 life.

Nurturing Peatland

{T}, Pay 1 life: Add {B} or {G}.
{1}, {T}, Sacrifice Nurturing Peatland: Draw a card.

Verdant Catacombs

{T}, Pay 1 life, Sacrifice Verdant Catacombs: Search your library for a Swamp or Forest card, put it onto the battlefield, then shuffle.

Sign in Blood

Target player draws two cards and loses 2 life.

Vampire's Kiss

Target player loses 2 life and you gain 2 life. Create two Blood tokens. (They're artifacts with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")

Bump in the Night

Target opponent loses 3 life.
Flashback {5}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Blood Crypt

({T}: Add {B} or {R}.)
As Blood Crypt enters, you may pay 2 life. If you don't, it enters tapped.

Nezumi Road Captain

Menace
Vehicles you control have menace. (They can't be blocked except by two or more creatures.)

Okiba Reckoner Raid

(As this Saga enters and after your draw step, add a lore counter.)
I, II — Each opponent loses 1 life and you gain 1 life.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Okiba Reckoner Raid // Nezumi Road Captain

Silent Clearing

{T}, Pay 1 life: Add {W} or {B}.
{1}, {T}, Sacrifice Silent Clearing: Draw a card.

Gonti's Machinations

Whenever you lose life for the first time each turn, you get {E}. (You get an energy counter. Damage causes loss of life.)
Pay {E}{E}, Sacrifice Gonti's Machinations: Each opponent loses 3 life. You gain life equal to the life lost this way.

Sword-Point Diplomacy

Reveal the top three cards of your library. For each of those cards, put that card into your hand unless any opponent pays 3 life. Then exile the rest.

Swamp

Soul Spike

You may exile two black cards from your hand rather than pay this spell's mana cost.
Soul Spike deals 4 damage to any target and you gain 4 life.

Chancellor of the Dross

You may reveal this card from your opening hand. If you do, at the beginning of the first upkeep, each opponent loses 3 life, then you gain life equal to the life lost this way.
Flying, lifelink

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Sleeper Agent

When Sleeper Agent enters, target opponent gains control of it.
At the beginning of your upkeep, Sleeper Agent deals 2 damage to you.