Exquisite Blood

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

Swamp

Leechridden Swamp

({T}: Add {B}.)
This land enters tapped.
{B}, {T}: Each opponent loses 1 life. Activate only if you control two or more black permanents.

Bloodghast

This creature can't block.
This creature has haste as long as an opponent has 10 or less life.
Landfall — Whenever a land you control enters, you may return this card from your graveyard to the battlefield.

Vito, Thorn of the Dusk Rose

Whenever you gain life, target opponent loses that much life.
{3}{B}{B}: Creatures you control gain lifelink until end of turn.

Bloodthirsty Aerialist

Flying
Whenever you gain life, put a +1/+1 counter on this creature.

Sorin, Vampire Lord

+1: Up to one target creature gets +2/+0 until end of turn.
−2: Sorin deals 4 damage to any target. You gain 4 life.
−8: Until end of turn, each Vampire you control gains "{T}: Gain control of target creature."

Marauding Blight-Priest

Whenever you gain life, each opponent loses 1 life.

Vampire of the Dire Moon

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Sanguine Bond

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

Sorin's Guide

When this creature enters, you may search your library and/or graveyard for a card named Sorin, Vampire Lord, reveal it, and put it into your hand. If you search your library this way, shuffle.