Olivia's Midnight Ambush

Target creature gets -2/-2 until end of turn. If it's night, that creature gets -13/-13 until end of turn instead.

Mountain

Vampire Socialite

Menace (This creature can't be blocked except by two or more creatures.)
When this creature enters, if an opponent lost life this turn, put a +1/+1 counter on each other Vampire you control.
As long as an opponent lost life this turn, each other Vampire you control enters with an additional +1/+1 counter on it.

Hungry for More

Create a 3/1 black and red Vampire creature token with trample, lifelink, and haste. Sacrifice it at the beginning of the next end step.
Flashback {1}{B}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Bat Whisperer

When this creature enters, if an opponent lost life this turn, create a 1/1 black Bat creature token with flying.

Vampire Interloper

Voldaren Stinger

This creature has first strike as long as it's attacking.
{2}{R}: This creature gets +2/+0 until end of turn.

Falkenrath Pit Fighter

{1}{R}, Discard a card, Sacrifice a Vampire: Draw two cards. Activate only if an opponent lost life this turn.

Haunted Ridge

This land enters tapped unless you control two or more other lands.
{T}: Add {B} or {R}.

Stromkirk Bloodthief

At the beginning of your end step, if an opponent lost life this turn, put a +1/+1 counter on target Vampire you control.

Neonate's Rush

This spell costs {1} less to cast if you control a Vampire.
Neonate's Rush deals 1 damage to target creature and 1 damage to its controller. Draw a card.

Swamp

Florian, Voldaren Scion

First strike
At the beginning of each of your postcombat main phases, look at the top X cards of your library, where X is the total amount of life your opponents lost this turn. Exile one of those cards and put the rest on the bottom of your library in a random order. You may play the exiled card this turn.

Voldaren Ambusher

When this creature enters, if an opponent lost life this turn, it deals X damage to up to one target creature or planeswalker, where X is the number of Vampires you control.