Counterspell

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.

Sol Ring

Murktide Regent

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Flying
Murktide Regent enters with a +1/+1 counter on it for each instant and sorcery card exiled with it.
Whenever an instant or sorcery card leaves your graveyard, put a +1/+1 counter on Murktide Regent.

Witch's Vengeance

Creatures of the creature type of your choice get -3/-3 until end of turn.

Diabolic Edict

Target player sacrifices a creature of their choice.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Temple of Deceit

Temple of Deceit enters tapped.
When Temple of Deceit enters, scry 1.
{T}: Add {U} or {B}.

Darkwater Catacombs

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Island

Command Tower

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

Bad Moon

Field of Ruin

{T}: Add {C}.
{2}, {T}, Sacrifice Field of Ruin: Destroy target nonbasic land an opponent controls. Each player searches their library for a basic land card, puts it onto the battlefield, then shuffles.

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Go for the Throat

Languish

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

Bojuka Bog

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

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. Talisman of Dominance deals 1 damage to you.

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Slaughter Pact

Destroy target nonblack creature.
At the beginning of your next upkeep, pay {2}{B}. If you don't, you lose the game.

Voracious Fell Beast

Flying
When Voracious Fell Beast enters, each opponent sacrifices a creature of their choice. Create a Food token for each creature sacrificed this way. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

Lord of the Nazgûl

Flying
Wraiths you control have protection from Ring-bearers.
Whenever you cast an instant or sorcery spell, create a 3/3 black Wraith creature token with menace. Then if you control nine or more Wraiths, Wraiths you control have base power and toughness 9/9 until end of turn.

Swamp

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.

Charcoal Diamond

Charcoal Diamond enters tapped.
{T}: Add {B}.

Beacon of Unrest

Put target artifact or creature card from a graveyard onto the battlefield under your control. Shuffle Beacon of Unrest into its owner's library.

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.

Rona, Sheoldred's Faithful

Whenever you cast an instant or sorcery spell, each opponent loses 1 life.
You may cast Rona, Sheoldred's Faithful from your graveyard by discarding two cards in addition to paying its other costs.