Cordial Vampire

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

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

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.)

Promise of Aclazotz // Foul Rebirth

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.

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.)

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.)