Explore the Underdark

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.
You take the initiative.

Banishing Coils

Exile target artifact or enchantment. (Then exile this card. You may cast the creature later from exile.)

Guardian Naga

Vigilance
During your turn, prevent all damage that would be dealt to this creature.

Guardian Naga // Banishing Coils

Fire Diamond

This artifact enters tapped.
{T}: Add {R}.

Thieves' Tools

When this Equipment enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Equipped creature can't be blocked as long as its power is 3 or less.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Dig Deep

Choose target creature. Mill four cards, then put a +1/+1 counter on that creature for each creature card milled this way.

Colossal Badger

When this creature enters, you gain 3 life.

Colossal Badger // Dig Deep

Recruitment Drive

Roll a d20.
1—9 | Create two 1/1 white Soldier creature tokens.
10—19 | Create two 2/2 white Knight creature tokens.
20 | Create three 2/2 white Knight creature tokens.

Insufferable Balladeer

Vicious Mockery — When this creature enters, target creature an opponent controls can't block this turn. Goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Underdark Explorer

Menace (This creature can't be blocked except by two or more creatures.)
When this creature enters, you take the initiative.

Draconic Muralists

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

Kagha, Shadow Archdruid

Whenever Kagha attacks, it gains deathtouch until end of turn. Mill two cards. (Put the top two cards of your library into your graveyard.)
Once during each of your turns, you may play a land or cast a permanent spell from among cards in your graveyard that were put there from your library this turn.

Undercellar Sweep

When this enchantment enters, you take the initiative.
Whenever you attack, if you or a player you're attacking has the initiative, you create two 1/1 white Soldier creature tokens that are tapped and attacking.

Amber Gristle O'Maul

Haste
Whenever Amber Gristle O'Maul attacks, you may discard your hand. If you do, draw a card for each player being attacked.
Choose a Background (You can have a Background as a second commander.)

Dynaheir, Invoker Adept

Haste
You may activate abilities of other creatures you control as though those creatures had haste.
{T}: When you next activate an ability that isn't a mana ability this turn by spending four or more mana to activate it, copy that ability. You may choose new targets for the copy.

Tiamat's Fanatics

Haste
Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Goliath Paladin

Vigilance
When this creature enters, you take the initiative.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Firbolg Flutist

Enthralling Performance — When this creature enters, gain control of target creature you don't control until end of turn. Untap it. It gains haste and myriad until end of turn. (Whenever it attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Tyr's Blessing

Target creature gains indestructible until end of turn. (Then exile this card. You may cast the creature later from exile.)

Blessed Hippogriff

Flying
Whenever this creature attacks, target attacking creature without flying gains flying until end of turn.

Blessed Hippogriff // Tyr's Blessing

Jade Orb of Dragonkind

{T}: Add {G}. When you spend this mana to cast a Dragon creature spell, it enters with an additional +1/+1 counter on it and gains hexproof until your next turn. (It can't be the target of spells or abilities your opponents control.)

Mold Folk

Lifelink
Mold Harvest — {1}, Sacrifice another creature or an artifact: Put a +1/+1 counter on this creature.

Earth Tremor

Earth Tremor deals damage to target creature or planeswalker equal to the number of lands you control.

Skullport Merchant

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
{1}{B}, Sacrifice another creature or a Treasure: Draw a card.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Aquatic Ingress

Up to two target creatures each get +1/+0 until end of turn and can't be blocked this turn. (Then exile this card. You may cast the creature later from exile.)

Sea Hag

When this creature enters, creatures your opponents control get -4/-0 until end of turn.

Sea Hag // Aquatic Ingress

Murder

Oceanus Dragon

Flying
When this creature enters, tap target creature an opponent controls. Goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Mahadi, Emporium Master

At the beginning of your end step, create a Treasure token for each creature that died this turn. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Astral Confrontation

This spell costs {1} less to cast for each opponent you're attacking.
Exile target creature.

Tavern Brawler

Commander creatures you own have "At the beginning of your upkeep, exile the top card of your library. This creature gets +X/+0 until end of turn, where X is that card's mana value. You may play that card this turn."

Prized Statue

When this artifact enters or is put into a graveyard from the battlefield, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Kenku Artificer

Homunculus Servant — When this creature enters, put three +1/+1 counters on up to one target noncreature artifact. That artifact becomes a 0/0 Homunculus artifact creature with flying.

Ambition's Cost

You draw three cards and you lose 3 life.

Marut

Trample
When this creature enters, if mana from a Treasure was spent to cast it, create a Treasure token for each mana from a Treasure spent to cast it. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Ghastly Death Tyrant

When this creature enters, choose one —
• Disintegration Ray — Destroy target enchantment an opponent controls. You lose life equal to its mana value.
• Death Ray — Creatures you control gain deathtouch until end of turn.

Carefree Swinemaster

Whenever this creature attacks, you may pay {1}{G}. If you do, create a 2/2 green Boar creature token that's tapped and attacking.

Black Dragon Gate

This land enters tapped.
As this land enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Basilisk Gate

{T}: Add {C}.
{2}, {T}: Target creature gets +X/+X until end of turn, where X is the number of Gates you control. Activate only as a sorcery.

Roving Harper

Sigil of Myrkul

At the beginning of combat on your turn, mill a card. When you do, if there are four or more creature cards in your graveyard, put a +1/+1 counter on target creature you control and it gains deathtouch until end of turn. (To mill a card, put the top card of your library into your graveyard.)

Charcoal Diamond

This artifact enters tapped.
{T}: Add {B}.

Acolyte of Bahamut

Commander creatures you own have "The first Dragon spell you cast each turn costs {2} less to cast."

Genasi Enforcers

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
{1}{R}: Creatures you control named Genasi Enforcers get +1/+0 until end of turn.

Prophetic Prism

When this artifact enters, draw a card.
{1}, {T}: Add one mana of any color.

Noble Heritage

Commander creatures you own have "When this creature enters and at the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. For each opponent who does, you gain protection from that player until your next turn." (You can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Vicious Battlerager

When this creature enters, you take the initiative.
Spiked Retribution — Whenever this creature becomes blocked by a creature, that creature's controller loses 5 life.

Candlekeep Sage

Commander creatures you own have "When this creature enters or leaves the battlefield, draw a card."

Forktail Sweep

Forktail Sweep deals 1 damage to each creature you don't control. (Then exile this card. You may cast the creature later from exile.)

Fang Dragon

Fang Dragon // Forktail Sweep

Cast Down

Safana, Calimport Cutthroat

Menace
At the beginning of your end step, if you have the initiative, create a Treasure token. Create three of those tokens instead if you've completed a dungeon.
Choose a Background (You can have a Background as a second commander.)

Sea Gate

This land enters tapped.
As this land enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Druidic Ritual

You may mill three cards. Then return up to one creature card and up to one land card from your graveyard to your hand. (To mill a card, put the top card of your library into your graveyard.)

Shiny Impetus

Enchant creature
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)
Whenever enchanted creature attacks, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Lurking Green Dragon

Flying
This creature can't attack unless defending player controls a creature with flying.

Nimblewright Schematic

When this artifact enters or is put into a graveyard from the battlefield, create a 1/1 colorless Construct artifact creature token.

Cloak of the Bat

Equipped creature has flying and haste.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Cloakwood Swarmkeeper

Gathered Swarm — Whenever one or more tokens you control enter, put a +1/+1 counter on this creature.

Predatory Impetus

Enchant creature
Enchanted creature gets +3/+3, must be blocked if able, and is goaded. (It attacks each combat if able and attacks a player other than you if able.)

Nimbleclaw Adept

Bigby's Hand — {T}: Untap two other target permanents. Activate only as a sorcery and only once each turn.

Parasitic Impetus

Enchant creature
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)
Whenever enchanted creature attacks, its controller loses 2 life and you gain 2 life.

Clockwork Fox

When this creature leaves the battlefield, you draw two cards and each opponent draws a card.

Myrkul's Invoker

Psychic Blades — {8}: Creatures you control get +2/+0 and gain menace until end of turn. (A creature with menace can't be blocked except by two or more creatures.)

Tymora's Invoker

Bloodboil Sorcerer

When this creature enters, you take the initiative.
Crown of Madness — {1}{R}, Sacrifice an artifact or creature: Goad target creature. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Rescue the Foal

Exile target creature you control, then return that card to the battlefield under its owner's control. (Then exile this card. You may cast the creature later from exile.)

Pegasus Guardian

Flying
At the beginning of your end step, if a permanent you controlled left the battlefield this turn, create a 1/1 white Pegasus creature token with flying.

Pegasus Guardian // Rescue the Foal

Lozhan, Dragons' Legacy

Flying
Whenever you cast an Adventure or Dragon spell, Lozhan deals damage equal to that spell's mana value to any target that isn't a commander.

Silvanus's Invoker

Conjure Elemental — {8}: Untap target land you control. It becomes an 8/8 Elemental creature with trample and haste until end of turn. It's still a land.

Web Shot

Destroy target creature with flying. (Then exile this card. You may cast the creature later from exile.)

Ettercap

Ettercap // Web Shot

Your Temple Is Under Attack

Choose one —
• Pray for Protection — Creatures you control gain indestructible until end of turn.
• Strike a Deal — You and target opponent each draw two cards.

Ysgard's Call

Create X 1/1 white Soldier creature tokens. (Then exile this card. You may cast the artifact later from exile.)

Horn of Valhalla

Equipped creature gets +1/+1 for each creature you control.
Equip {3}

Horn of Valhalla // Ysgard's Call

Reckless Barbarian

Javelin of Lightning

Flash
When this Equipment enters, attach it to target creature you control.
During your turn, equipped creature gets +2/+0 and has first strike.
Equip {4} ({4}: Attach to target creature you control. Equip only as a sorcery.)

Elminster's Simulacrum

For each opponent, you create a token that's a copy of up to one target creature that player controls.

Cut a Deal

Each opponent draws a card, then you draw a card for each opponent who drew a card this way.

Ascend from Avernus

Return all creature and planeswalker cards with mana value X or less from your graveyard to the battlefield. Exile Ascend from Avernus.

Stirring Bard

Defender
When this creature enters, you take the initiative.
Mantle of Inspiration — {T}: Target creature gains menace and haste until end of turn.

Nothic

Weird Insight — When this creature dies, roll a d20.
1—9 | You draw a card and you lose 1 life.
10—19 | You draw two cards and you lose 2 life.
20 | You draw seven cards and you lose 7 life.