Eternal Thirst

Enchant creature
Enchanted creature has lifelink and "Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature." (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Swamp

Vampire Opportunist

{6}{B}: Each opponent loses 2 life and you gain 2 life.

Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Malakir Cullblade

Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature.

Savage Gorger

Flying
At the beginning of your end step, if an opponent lost life this turn, put a +1/+1 counter on this creature. (Damage causes loss of life.)

Compound Fracture

Target creature gets -1/-1 until end of turn. It gets an additional -1/-1 until end of turn for each card named Compound Fracture in your graveyard.

Unlikely Aid

Target creature gets +2/+0 and gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Sanitarium Skeleton

{2}{B}: Return this card from your graveyard to your hand.

Cruel Cut

Destroy target creature with power 2 or less.

Mardu Outrider

As an additional cost to cast this spell, discard a card.

Demon of Loathing

Flying, trample
Whenever this creature deals combat damage to a player, that player sacrifices a creature of their choice.

Sengir Vampire

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a creature dealt damage by this creature this turn dies, put a +1/+1 counter on this creature.

Bad Deal

You draw two cards and each opponent discards two cards. Each player loses 2 life.