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.)

Heir to the Night

Heir of Falkenrath

Discard a card: Transform Heir of Falkenrath. Activate only once each turn.

Heir of Falkenrath // Heir to the Night

Cordial Vampire

Whenever Cordial Vampire or another creature dies, put a +1/+1 counter on each Vampire you control.

Dusk Legion Sergeant

Menace
{1}{B}, Sacrifice Dusk Legion Sergeant: Each nontoken Vampire creature you control gains persist until end of turn. (When it dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Bloodghast

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

Stromkirk Condemned

Discard a card: Vampires you control get +1/+1 until end of turn. Activate only once each turn.

Foul Rebirth

Sacrifice a non-Demon creature. If you do, create a 4/3 white and black Vampire Demon creature token with flying.

Promise of Aclazotz

At the beginning of your end step, you may sacrifice a non-Demon creature. If you do, populate. (Create a token that's a copy of a creature token you control.)