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.)

Bloodthrone Vampire

Sacrifice a creature: Bloodthrone Vampire gets +2/+2 until end of turn.

Ruthless Cullblade

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

Mindless Null

Mindless Null can't block unless you control a Vampire.

Blood Seeker

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

Bloodrage Vampire

Bloodthirst 1 (If an opponent was dealt damage this turn, this creature enters with a +1/+1 counter on it.)

Bloodbond Vampire

Whenever you gain life, put a +1/+1 counter on Bloodbond Vampire.

Vampire Lacerator

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

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.)
Quag Vampires enters with a +1/+1 counter on it for each time it was kicked.

Bloodhusk Ritualist

Multikicker {B} (You may pay an additional {B} any number of times as you cast this spell.)
When Bloodhusk Ritualist enters, target opponent discards a card for each time it was kicked.

Vampire Aristocrat

Sacrifice a creature: Vampire Aristocrat gets +2/+2 until end of turn.

Vampire Outcasts

Bloodthirst 2 (If an opponent was dealt damage this turn, this creature enters with two +1/+1 counters on it.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Child of Night

Kelinore Bat

Pulse Tracker

Whenever this creature attacks, each opponent loses 1 life.

Bloodflow Connoisseur

Sacrifice a creature: Put a +1/+1 counter on Bloodflow Connoisseur.

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.)