Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Rowan, Scion of War

Menace
{T}: Spells you cast this turn that are black and/or red cost {X} less to cast, where X is the amount of life you lost this turn. Activate only as a sorcery.

Orcus, Prince of Undeath

Flying, trample
When Orcus, Prince of Undeath enters, choose one —
• Each other creature gets -X/-X until end of turn. You lose X life.
• Return up to X target creature cards with total mana value X or less from your graveyard to the battlefield. They gain haste until end of turn.

Font of Agonies

Whenever you pay life, put that many blood counters on Font of Agonies.
{1}{B}, Remove four blood counters from Font of Agonies: Destroy target creature.

Deepwood Ghoul

Greven, Predator Captain

Menace
Greven, Predator Captain gets +X/+0, where X is the amount of life you've lost this turn.
Whenever Greven attacks, you may sacrifice another creature. If you do, you draw cards equal to that creature's power and you lose life equal to that creature's toughness.

Tavern Swindler

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

Sanguine Bond

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

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Stormfist Crusader

Menace
At the beginning of your upkeep, each player draws a card and loses 1 life.

Exsanguinate

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

Dark Ritual

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.