Malcolm, Keen-Eyed Navigator

Flying
Whenever one or more Pirates you control deal damage to your opponents, you create a Treasure token for each opponent dealt damage. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Partner (You can have two commanders if both have partner.)

Cauldron of Souls

{T}: Choose any number of target creatures. Each of those creatures gains persist until end of turn. (When it dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Master of the Pearl Trident

Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Universal Automaton

Changeling (This card is every creature type.)

Ertai Resurrected

Flash
When Ertai Resurrected enters, choose up to one —
• Counter target spell, activated ability, or triggered ability. Its controller draws a card.
• Destroy another target creature or planeswalker. Its controller draws a card.

Bojuka Bog

This land enters tapped.
When this land enters, exile target player's graveyard.
{T}: Add {B}.

Absorb Identity

Return target creature to its owner's hand. You may have Shapeshifters you control become copies of that creature until end of turn.

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Volo, Itinerant Scholar

When Volo enters, create Volo's Journal, a legendary colorless artifact token with hexproof and "Whenever you cast a creature spell, note one of its creature types that hasn't been noted for Volo's Journal."
{2}, {T}: Draw a card for each creature type noted for target permanent you control named Volo's Journal.
Choose a Background

Command Tower

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

Araumi of the Dead Tide

{T}, Exile cards from your graveyard equal to the number of opponents you have: Target creature card in your graveyard gains encore until end of turn. The encore cost is equal to its mana cost. (Exile the creature card and pay its mana cost: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Darkwater Catacombs

Mistform Ultimus

Mistform Ultimus is every creature type (even if this card isn't on the battlefield).

Mist Dancer

Flying
Other Merfolk you control get +1/+0 and have flying.
Encore {5}{U}{U} ({5}{U}{U}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Relic of Legends

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

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Scion of Oona

Flash
Flying
Other Faerie creatures you control get +1/+1.
Other Faeries you control have shroud. (They can't be the targets of spells or abilities.)

Deadeye Tracker

{1}{B}, {T}: Exile two target cards from an opponent's graveyard. This creature explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Hostage Taker

When this creature enters, exile another target creature or artifact until this creature leaves the battlefield. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

Corsair Captain

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Other Pirates you control get +1/+1.

Swamp

Venomous Changeling

Changeling (This card is every creature type.)
Deathtouch

Prosperous Thief

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever one or more Ninja or Rogue creatures you control deal combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Ramses, Assassin Lord

Deathtouch
Other Assassins you control get +1/+1.
Whenever a player loses the game, if they were attacked this turn by an Assassin you controlled, you win the game.

Sage of Fables

Each other Wizard creature you control enters with an additional +1/+1 counter on it.
{2}, Remove a +1/+1 counter from a creature you control: Draw a card.

Amoeboid Changeling

Changeling (This card is every creature type.)
{T}: Target creature gains all creature types until end of turn.
{T}: Target creature loses all creature types until end of turn.

Sting, the Glinting Dagger

Equipped creature gets +1/+1 and has haste.
At the beginning of each combat, untap equipped creature.
Equipped creature has first strike as long as it's blocking or blocked by a Goblin or Orc.
Equip {2}

Moonglove Changeling

Changeling (This card is every creature type.)
{B}: This creature gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy that creature.)

Arcane Signet

Wayfarer's Bauble

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

Nameless Inversion

Changeling (This card is every creature type.)
Target creature gets +3/-3 and loses all creature types until end of turn.

Mistwalker

Changeling (This card is every creature type.)
Flying
{1}{U}: This creature gets +1/-1 until end of turn.

Exterminate!

Replicate—Tap an untapped Dalek you control. (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Destroy target creature. Its controller loses 3 life.

Burakos, Party Leader

Burakos is also a Cleric, Rogue, Warrior, and Wizard.
Whenever Burakos attacks, defending player loses X life and you create X Treasure tokens, where X is the number of creatures in your party.
Choose a Background (You can have a Background as a second commander.)

Haunted One

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Reflections of Littjara

As this enchantment enters, choose a creature type.
Whenever you cast a spell of the chosen type, copy that spell. (A copy of a permanent spell becomes a token.)

Ghostly Changeling

Changeling (This card is every creature type.)
{1}{B}: This creature gets +1/+1 until end of turn.

Lord of the Unreal

Illusion creatures you control get +1/+1 and have hexproof. (They can't be the targets of spells or abilities your opponents control.)

Negate

Ramirez DePietro, Pillager

When Ramirez DePietro enters, you lose 2 life and create two Treasure tokens.
Whenever one or more Pirates you control deal combat damage to a player, exile the top card of that player's library. You may cast that card for as long as it remains exiled.

Markov Baron

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Lifelink
Other Vampires you control get +1/+1.
Madness {2}{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.)

Birthing Boughs

{4}, {T}: Create a 2/2 colorless Shapeshifter creature token with changeling. (It is every creature type.)

Littjara Kinseekers

Changeling (This card is every creature type.)
When this creature enters, if you control three or more creatures that share a creature type, put a +1/+1 counter on this creature, then scry 1.

Bloodline Necromancer

Lifelink
When this creature enters, you may return target Vampire or Wizard creature card from your graveyard to the battlefield.

Bloodline Pretender

Changeling (This card is every creature type.)
As this creature enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on this creature.

Crux of Fate

Choose one —
• Destroy all Dragon creatures.
• Destroy all non-Dragon creatures.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Tegwyll, Duke of Splendor

Flying, deathtouch
Other Faeries you control get +1/+1.
Whenever another Faerie you control dies, you draw a card and you lose 1 life.

Cursecatcher

Sacrifice this creature: Counter target instant or sorcery spell unless its controller pays {1}.

Soul Diviner

{T}, Remove a counter from an artifact, creature, land, or planeswalker you control: Draw a card.

Merchant Raiders

Whenever this creature or another Pirate you control enters, tap up to one target creature. That creature doesn't untap during its controller's untap step for as long as you control this creature.

Graveshifter

Changeling (This card is every creature type.)
When this creature enters, you may return target creature card from your graveyard to your hand.

Island

Skeletal Changeling

Changeling (This card is every creature type.)
{1}{B}: Regenerate this creature.

Turtleshell Changeling

Changeling (This card is every creature type.)
{1}{U}: Switch this creature's power and toughness until end of turn.

Merrow Reejerey

Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.

Hibernation Sliver

All Slivers have "Pay 2 life: Return this permanent to its owner's hand."

Retribution of the Ancients

{B}, Remove X +1/+1 counters from among creatures you control: Target creature gets -X/-X until end of turn.

Thief of Blood

Flying
As this creature enters, remove all counters from all permanents. This creature enters with a +1/+1 counter on it for each counter removed this way.

Azami, Lady of Scrolls

Tap an untapped Wizard you control: Draw a card.

Mistcaller

Sacrifice this creature: Until end of turn, if a nontoken creature would enter and it wasn't cast, exile it instead.

Choked Estuary

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

Siren Stormtamer

Flying
{U}, Sacrifice this creature: Counter target spell or ability that targets you or a creature you control.

Glen Elendra Liege

Flying
Other blue creatures you control get +1/+1.
Other black creatures you control get +1/+1.

Yuriko, the Tiger's Shadow

Commander ninjutsu {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand or the command zone tapped and attacking.)
Whenever a Ninja you control deals combat damage to a player, reveal the top card of your library and put that card into your hand. Each opponent loses life equal to that card's mana value.

Runed Stalactite

Equipped creature gets +1/+1 and is every creature type.
Equip {2}

The Grim Captain

Menace, trample, lifelink, hexproof
Whenever The Grim Captain attacks, each opponent sacrifices a nonland permanent of their choice. Then you may put an exiled creature card used to craft The Grim Captain onto the battlefield under your control tapped and attacking.

Throne of the Grim Captain

{T}: Mill two cards.
Craft with a Dinosaur, a Merfolk, a Pirate, and a Vampire {4} ({4}, Exile this artifact, Exile the four from among permanents you control and/or cards in your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.)

Throne of the Grim Captain // The Grim Captain

Dimir Signet

Mothdust Changeling

Changeling (This card is every creature type.)
Tap an untapped creature you control: This creature gains flying until end of turn.

Thought Vessel

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

Crypt Sliver

All Slivers have "{T}: Regenerate target Sliver."

Peer Pressure

Choose a creature type. If you control more creatures of that type than each other player, you gain control of all creatures of that type. (This effect lasts indefinitely.)

Changeling Outcast

Changeling (This card is every creature type.)
This creature can't block and can't be blocked.