Grasp of Darkness

Target creature gets -4/-4 until end of turn.

Blood Seeker

Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Guul Draz Vampire

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

Unholy Strength

Enchant creature
Enchanted creature gets +2/+1.

Swamp

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Disfigure

Target creature gets -2/-2 until end of turn.

Diabolic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Feast of Blood

Cast this spell only if you control two or more Vampires.
Destroy target creature. You gain 4 life.

Underworld Dreams

Whenever an opponent draws a card, this enchantment deals 1 damage to that player.

Doom Blade

Quag Vampires

Multikicker {1}{B} (You may pay an additional {1}{B} any number of times as you cast this spell.)
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
This creature enters with a +1/+1 counter on it for each time it was kicked.

Drana, Kalastria Bloodchief

Flying
{X}{B}{B}: Target creature gets -0/-X until end of turn and Drana gets +X/+0 until end of turn.

Dark Ritual

Vampire Nighthawk

Flying
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.)

Captivating Vampire

Other Vampire creatures you control get +1/+1.
Tap five untapped Vampires you control: Gain control of target creature. It becomes a Vampire in addition to its other types.