Sol Ring

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.

Karn's Bastion

{T}: Add {C}.
{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Black Dragon Gate

Black Dragon Gate enters tapped.
As Black Dragon Gate enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Languish

All creatures get -4/-4 until end of turn.

Mutilate

All creatures get -1/-1 until end of turn for each Swamp you control.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Agent of the Shadow Thieves

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, put a +1/+1 counter on this creature. It gains deathtouch and indestructible until end of turn."

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Withering Torment

Destroy target creature or enchantment. You lose 2 life.

Decree of Pain

Destroy all creatures. They can't be regenerated. Draw a card for each creature destroyed this way.
Cycling {3}{B}{B} ({3}{B}{B}, Discard this card: Draw a card.)
When you cycle Decree of Pain, all creatures get -2/-2 until end of turn.

Giant Slug

{5}: At the beginning of your next upkeep, choose a basic land type. Giant Slug gains landwalk of the chosen type until the end of that turn. (It can't be blocked as long as defending player controls a land of that type.)

Abnormal Endurance

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control."

Evolving Wilds

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

Gluttonous Slug

Menace
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Afflict

Target creature gets -1/-1 until end of turn.
Draw a card.

Bojuka Bog

Bojuka Bog enters tapped.
When Bojuka Bog enters, exile target player's graveyard.
{T}: Add {B}.

Arcane Signet

Catacomb Slug

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Alms of the Vein

Target opponent loses 3 life and you gain 3 life.
Madness {B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Morkrut Necropod

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Morkrut Necropod attacks or blocks, sacrifice another creature or land.

Swamp

Archway Commons

Archway Commons enters tapped.
When Archway Commons enters, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

Whisper of the Dross

Target creature gets -1/-1 until end of turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)