Toxin Analysis

Target creature gains deathtouch and lifelink until end of turn. Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Wedding Invitation

When Wedding Invitation enters, draw a card.
{T}, Sacrifice Wedding Invitation: Target creature can't be blocked this turn. If it's a Vampire, it also gains lifelink until end of turn.

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.)

Falkenrath Noble

Flying
Whenever Falkenrath Noble or another creature dies, target player loses 1 life and you gain 1 life.

Swamp

Vampire Spawn

When this creature enters, each opponent loses 2 life and you gain 2 life.

Blood Seeker

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

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Tithe Drinker

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Marauding Blight-Priest

Whenever you gain life, each opponent loses 1 life.

Vampire Sovereign

Flying
When Vampire Sovereign enters, target opponent loses 3 life and you gain 3 life.

Cloudshift

Exile target creature you control, then return that card to the battlefield under your control.

Creeping Bloodsucker

At the beginning of your upkeep, Creeping Bloodsucker deals 1 damage to each opponent. You gain life equal to the damage dealt this way.