Toxrill, the Corrosive

At the beginning of each end step, put a slime counter on each creature you don't control.
Creatures you don't control get -1/-1 for each slime counter on them.
Whenever a creature you don't control with a slime counter on it dies, create a 1/1 black Slug creature token.
{U}{B}, Sacrifice a Slug: Draw a card.

Swamp

Overcharged Amalgam

Flash
Flying
Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, counter target spell, activated ability, or triggered ability.

Island

Headless Rider

Whenever this creature or another nontoken Zombie you control dies, create a 2/2 black Zombie creature token.

Wretched Throng

When this creature dies, you may search your library for a card named Wretched Throng, reveal it, put it into your hand, then shuffle.

Archghoul of Thraben

Whenever this creature or another Zombie you control dies, look at the top card of your library. If it's a Zombie card, you may reveal it and put it into your hand. If you don't put the card into your hand, you may put it into your graveyard.

Mindleech Ghoul

Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, each opponent exiles a card from their hand.

Undead Butler

When this creature enters, mill three cards. (Put the top three cards of your library into your graveyard.)
When this creature dies, you may exile it. When you do, return target creature card from your graveyard to your hand.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Necroduality

Whenever a nontoken Zombie you control enters, create a token that's a copy of that creature.

Doomed Dissenter

When this creature dies, create a 2/2 black Zombie creature token.

Skull Skaab

Exploit (When this creature enters, you may sacrifice a creature.)
Whenever a creature you control exploits a nontoken creature, create a 2/2 black Zombie creature token.

Fell Stinger

Deathtouch
Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, target player draws two cards and loses 2 life.

Geralf, Visionary Stitcher

Zombies you control have flying.
{U}, {T}, Sacrifice another nontoken creature: Create an X/X blue Zombie creature token, where X is the sacrificed creature's toughness.

Dollhouse of Horrors

{1}, {T}, Exile a creature card from your graveyard: Create a token that's a copy of the exiled card, except it's a 0/0 Construct artifact in addition to its other types and it has "This token gets +1/+1 for each Construct you control." It gains haste until end of turn. Activate only as a sorcery.