Ruthless Cullblade

Ruthless Cullblade gets +2/+1 as long as an opponent has 10 or less life.

Sovereign's Bite

Target player loses 3 life and you gain 3 life.

Pulse Tracker

Whenever this creature attacks, each opponent loses 1 life.

Guul Draz Vampire

As long as an opponent has 10 or less life, Guul Draz Vampire gets +2/+1 and has intimidate. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)

Fruit of Tizerus

Target player loses 2 life.
Escape—{3}{B}, Exile three other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Geth's Verdict

Target player sacrifices a creature of their choice and loses 1 life.

Changeling Outcast

Changeling (This card is every creature type.)
Changeling Outcast can't block and can't be blocked.

Malakir Blood-Priest

When Malakir Blood-Priest enters, each opponent loses X life and you gain X life, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Sign in Blood

Target player draws two cards and loses 2 life.

Swamp

Vampire Lacerator

At the beginning of your upkeep, you lose 1 life unless an opponent has 10 or less life.

Morsel Theft

Prowl {1}{B} (You may cast this for its prowl cost if you dealt combat damage to a player this turn with a Rogue.)
Target player loses 3 life and you gain 3 life. If this spell's prowl cost was paid, draw a card.