Sinister Concoction

{B}, Pay 1 life, Mill a card, Discard a card, Sacrifice this enchantment: Destroy target creature.

Vona, Butcher of Magan

Vigilance, lifelink
{T}, Pay 7 life: Destroy target nonland permanent. Activate only during your turn.

Mask of Griselbrand

Equipped creature has flying and lifelink.
Whenever equipped creature dies, you may pay X life, where X is its power. If you do, draw X cards.
Equip {3}

Greed

Tymna the Weaver

Lifelink
At the beginning of each of your postcombat main phases, you may pay X life, where X is the number of opponents that were dealt combat damage this turn. If you do, draw X cards.
Partner (You can have two commanders if both have partner.)

Yawgmoth, Thran Physician

Protection from Humans
Pay 1 life, Sacrifice another creature: Put a -1/-1 counter on up to one target creature and draw a card.
{B}{B}, Discard a card: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Glass-Cast Heart

Whenever one or more Vampires you control attack, create a Blood token. (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this token: Draw a card.")
{B}, {T}, Pay 1 life: Create a 1/1 white and black Vampire creature token with lifelink.
{B}{B}, {T}, Sacrifice this artifact and thirteen Blood tokens: Each opponent loses 13 life and you gain 13 life.

Soul Kiss

Enchant creature
{B}, Pay 1 life: Enchanted creature gets +2/+2 until end of turn. Activate no more than three times each turn.

Forsworn Paladin

Menace
{1}{B}, {T}, Pay 1 life: Create a Treasure token.
{2}{B}: Target creature gets +2/+0 until end of turn. If mana from a Treasure was spent to activate this ability, that creature also gains deathtouch until end of turn.

Unspeakable Symbol

Pay 3 life: Put a +1/+1 counter on target creature.

Underworld Connections

Enchant land
Enchanted land has "{T}, Pay 1 life: Draw a card."

War Room

{T}: Add {C}.
{3}, {T}, Pay life equal to the number of colors in your commanders' color identity: Draw a card.

Underworld Coinsmith

Constellation — Whenever this creature or another enchantment you control enters, you gain 1 life.
{W}{B}, Pay 1 life: Each opponent loses 1 life.

Verrak, Warped Sengir

Flying, deathtouch, lifelink
Whenever you activate an ability that isn't a mana ability, if life was paid to activate it, you may pay that much life again. If you do, copy that ability. You may choose new targets for the copy.

K'rrik, Son of Yawgmoth

({B/P} can be paid with either {B} or 2 life.)
Lifelink
For each {B} in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.

Razaketh, the Foulblooded

Flying, trample
Pay 2 life, Sacrifice another creature: Search your library for a card, put that card into your hand, then shuffle.

Tivash, Gloom Summoner

Lifelink
At the beginning of your end step, if you gained life this turn, you may pay X life, where X is the amount of life you gained this turn. If you do, create an X/X black Demon creature token with flying.

Necropotence

Skip your draw step.
Whenever you discard a card, exile that card from your graveyard.
Pay 1 life: Exile the top card of your library face down. Put that card into your hand at the beginning of your next end step.

Tavern Swindler

{T}, Pay 3 life: Flip a coin. If you win the flip, you gain 6 life.

Grimclaw Bats

Flying
{B}, Pay 1 life: This creature gets +1/+1 until end of turn.

Martyrs' Tomb

Pay 2 life: Prevent the next 1 damage that would be dealt to target creature this turn.

Phyrexian Reclamation

{1}{B}, Pay 2 life: Return target creature 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.

Zhentarim Bandit

Whenever this creature attacks, you may pay 1 life. If you do, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")