Shadow Alley Denizen

Whenever another black creature you control enters, target creature gains intimidate until end of turn. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Aetherize

Return all attacking creatures to their owner's hand.

Bladebrand

Target creature gains deathtouch until end of turn.
Draw a card.

Keep Watch

Harrier Strix

Flying
When Harrier Strix enters, tap target permanent.
{2}{U}: Draw a card, then discard a card.

Sarevok, Deathbringer

At the beginning of each player's end step, if no permanents left the battlefield this turn, that player loses X life, where X is Sarevok's power.
Choose a Background (You can have a Background as a second commander.)

Ruin Raider

Raid — At the beginning of your end step, if you attacked this turn, reveal the top card of your library and put that card into your hand. You lose life equal to the card's mana value.

Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature of their choice.

Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

Thassa's Rebuff

Counter target spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Typhoid Rats

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

Arm with Aether

Until end of turn, creatures you control gain "Whenever this creature deals damage to an opponent, you may return target creature that player controls to its owner's hand."

Fall from Favor

Enchant creature
When Fall from Favor enters, tap enchanted creature and you become the monarch.
Enchanted creature doesn't untap during its controller's untap step unless that player is the monarch.

Grim Hireling

Whenever one or more creatures you control deal combat damage to a player, create two Treasure tokens.
{B}, Sacrifice X Treasures: Target creature gets -X/-X until end of turn. Activate only as a sorcery.

Shipwreck Singer

Flying
{1}{U}: Target creature an opponent controls attacks this turn if able.
{1}{B}, {T}: Attacking creatures get -1/-1 until end of turn.

Throne of the God-Pharaoh

At the beginning of your end step, each opponent loses life equal to the number of tapped creatures you control.

Mist-Cloaked Herald

Larceny

Whenever a creature you control deals combat damage to a player, that player discards a card.

Tale's End

Counter target activated ability, triggered ability, or legendary spell.

Scattering Stroke

Counter target spell. Clash with an opponent. If you win, at the beginning of your next main phase, you may add an amount of {C} equal to that spell's mana value. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Dimir Signet

Spectral Sailor

Flash (You may cast this spell any time you could cast an instant.)
Flying
{3}{U}: Draw a card.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Talisman of Dominance

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

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Sol Ring

Back for Seconds

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.)
Return up to two target creature cards from your graveyard to your hand. If this spell was bargained, you may put one of those cards with mana value 4 or less onto the battlefield instead of putting it into your hand.

Ashnod's Altar

Feywild Visitor

Commander creatures you own have "Whenever one or more nontoken creatures you control deal combat damage to a player, you create a 1/1 blue Faerie Dragon creature token with flying."

Baral's Expertise

Return up to three target artifacts and/or creatures to their owners' hands.
You may cast a spell with mana value 4 or less from your hand without paying its mana cost.

Call to the Void

Each player secretly chooses a creature they control and a creature they don't control. Then those choices are revealed. Destroy each creature chosen this way.

Negate

Aetherspouts

For each attacking creature, its owner puts it on their choice of the top or bottom of their library.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Dissolve

Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Mana Leak

Counter target spell unless its controller pays {3}.

Arcane Signet

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

Midnight Clock

{T}: Add {U}.
{2}{U}: Put an hour counter on Midnight Clock.
At the beginning of each upkeep, put an hour counter on Midnight Clock.
When the twelfth hour counter is put on Midnight Clock, shuffle your hand and graveyard into your library, then draw seven cards. Exile Midnight Clock.

Accursed Marauder

When Accursed Marauder enters, each player sacrifices a nontoken creature of their choice.

Counterspell

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Envelop

Virtus's Maneuver

For each player, choose friend or foe. Each friend returns a creature card from their graveyard to their hand. Each foe sacrifices a creature of their choice.

Necrobite

Target creature gains deathtouch until end of turn. Regenerate it. (The next time that creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Turn to Frog

Until end of turn, target creature loses all abilities and becomes a blue Frog with base power and toughness 1/1.