Dreamborn Muse

At the beginning of each player's upkeep, that player mills X cards, where X is the number of cards in their hand.

Khorvath's Fury

For each player, choose friend or foe. Each friend discards all cards from their hand, then draws that many cards plus one. Khorvath's Fury deals damage to each foe equal to the number of cards in their hand.

Thought Vessel

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

Empyrial Plate

Equipped creature gets +1/+1 for each card in your hand.
Equip {2}

Cecily, Haunted Mage

Your maximum hand size is eleven.
Whenever Cecily, Haunted Mage attacks, you draw a card and you lose 1 life. Then if you have eleven or more cards in your hand, you may cast an instant or sorcery spell from your hand without paying its mana cost.
Friends forever (You can have two commanders if both have friends forever.)

Tishana, Voice of Thunder

Tishana, Voice of Thunder's power and toughness are each equal to the number of cards in your hand.
You have no maximum hand size.
When Tishana enters, draw a card for each creature you control.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Kydele, Chosen of Kruphix

{T}: Add {C} for each card you've drawn this turn.
Partner (You can have two commanders if both have partner.)

Fellwar Stone

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

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Vial Smasher the Fierce

Whenever you cast your first spell each turn, choose an opponent at random. Vial Smasher the Fierce deals damage equal to that spell's mana value to that player or a planeswalker that player controls.
Partner (You can have two commanders if both have partner.)

Ivory Tower

At the beginning of your upkeep, you gain X life, where X is the number of cards in your hand minus 4.

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.

Mikokoro, Center of the Sea

{T}: Add {C}.
{2}, {T}: Each player draws a card.

Kagemaro, First to Suffer

Kagemaro, First to Suffer's power and toughness are each equal to the number of cards in your hand.
{B}, Sacrifice Kagemaro: All creatures get -X/-X until end of turn, where X is the number of cards in your hand.

Maro

Maro's power and toughness are each equal to the number of cards in your hand.

Ebony Owl Netsuke

At the beginning of each opponent's upkeep, if that player has seven or more cards in hand, Ebony Owl Netsuke deals 4 damage to that player.

Terramorphic Expanse

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

Meishin, the Mind Cage

All creatures get -X/-0, where X is the number of cards in your hand.

Cerebral Vortex

Target player draws two cards, then Cerebral Vortex deals damage to that player equal to the number of cards they've drawn this turn.

Forced Fruition

Whenever an opponent casts a spell, that player draws seven cards.

Forest

Edric, Spymaster of Trest

Whenever a creature deals combat damage to one of your opponents, its controller may draw a card.

Stormbreath Dragon

Flying, haste, protection from white
{5}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Stormbreath Dragon becomes monstrous, it deals damage to each opponent equal to the number of cards in that player's hand.

Werewolf of Ancient Hunger

Vigilance, trample
Werewolf of Ancient Hunger's power and toughness are each equal to the total number of cards in all players' hands.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Werewolf of Ancient Hunger.

Sage of Ancient Lore

Sage of Ancient Lore's power and toughness are each equal to the number of cards in your hand.
When Sage of Ancient Lore enters, draw a card.
At the beginning of each upkeep, if no spells were cast last turn, transform Sage of Ancient Lore.

Sage of Ancient Lore // Werewolf of Ancient Hunger

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Anvil of Bogardan

Players have no maximum hand size.
At the beginning of each player's draw step, that player draws an additional card, then discards a card.

Sol Ring

Sycorax Commander

First strike, haste
Sanctified Rules of Combat — When Sycorax Commander enters, each opponent faces a villainous choice — That opponent discards all the cards in their hand, then draws that many cards minus one, or Sycorax Commander deals damage to that player equal to the number of cards in their hand.

Font of Mythos

At the beginning of each player's draw step, that player draws two additional cards.

Hand of Vecna

At the beginning of combat on your turn, equipped creature or a creature you control named Vecna gets +X/+X until end of turn, where X is the number of cards in your hand.
Equip—Pay 1 life for each card in your hand.
Equip {2}

Scroll of Origins

{2}, {T}: Draw a card if you have seven or more cards in hand.

Viseling

At the beginning of each opponent's upkeep, Viseling deals X damage to that player, where X is the number of cards in their hand minus 4.

Reliquary Tower

Prosperity

Fevered Visions

At the beginning of each player's end step, that player draws a card. If the player is your opponent and has four or more cards in hand, Fevered Visions deals 2 damage to that player.

Black Vise

As Black Vise enters, choose an opponent.
At the beginning of the chosen player's upkeep, Black Vise deals X damage to that player, where X is the number of cards in their hand minus 4.

Counterspell

Folio of Fancies

Players have no maximum hand size.
{X}{X}, {T}: Each player draws X cards.
{2}{U}, {T}: Each opponent mills cards equal to the number of cards in their hand.

Exotic Orchard

Temple Bell

Dark Suspicions

At the beginning of each opponent's upkeep, that player loses X life, where X is the number of cards in that player's hand minus the number of cards in your hand.

Nekusar, the Mindrazer

At the beginning of each player's draw step, that player draws an additional card.
Whenever an opponent draws a card, Nekusar, the Mindrazer deals 1 damage to that player.

Arcane Signet

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

Island

Orcish Bowmasters

Flash
When Orcish Bowmasters enters and whenever an opponent draws a card except the first one they draw in each of their draw steps, Orcish Bowmasters deals 1 damage to any target. Then amass Orcs 1.

Psychosis Crawler

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.

Storm Seeker

Storm Seeker deals damage to target player equal to the number of cards in that player's hand.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Vicious Shadows

Whenever a creature dies, you may have Vicious Shadows deal damage to target player equal to the number of cards in that player's hand.

Misers' Cage

At the beginning of each opponent's upkeep, if that player has five or more cards in hand, Misers' Cage deals 2 damage to that player.

Teferi's Ageless Insight

If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Oppressive Will

Counter target spell unless its controller pays {1} for each card in your hand.

Dictate of Kruphix

Flash
At the beginning of each player's draw step, that player draws an additional card.

Sophic Centaur

{2}{G}{G}, {T}, Discard a card: You gain 2 life for each card in your hand.

Cultivate

Unquenchable Fury

Enchant creature
Enchanted creature has "Whenever this creature attacks, it deals X damage to defending player, where X is the number of cards in their hand."
When Unquenchable Fury is put into your graveyard from the battlefield, return it to your hand.

Masumaro, First to Live

Masumaro, First to Live's power and toughness are each equal to twice the number of cards in your hand.

Adamaro, First to Desire

Adamaro, First to Desire's power and toughness are each equal to the number of cards in the hand of the opponent with the most cards in hand.

Skullcage

At the beginning of each opponent's upkeep, Skullcage deals 2 damage to that player unless they have exactly three or exactly four cards in hand.

Inner Fire

Multani, Maro-Sorcerer

Shroud (This creature can't be the target of spells or abilities.)
Multani, Maro-Sorcerer's power and toughness are each equal to the total number of cards in all players' hands.

Tomoya the Revealer

{3}{U}{U}, {T}: Target player draws X cards, where X is the number of cards in your hand.

Jushi Apprentice

{2}{U}, {T}: Draw a card. If you have nine or more cards in hand, flip Jushi Apprentice.

Jushi Apprentice // Tomoya the Revealer

Sword of War and Peace

Equipped creature gets +2/+2 and has protection from red and from white.
Whenever equipped creature deals combat damage to a player, Sword of War and Peace deals damage to that player equal to the number of cards in their hand and you gain 1 life for each card in your hand.
Equip {2}

Rousing Refrain

Add {R} for each card in target opponent's hand. Until end of turn, you don't lose this mana as steps and phases end. Exile Rousing Refrain with three time counters on it.
Suspend 3—{1}{R} (Rather than cast this card from your hand, you may pay {1}{R} and exile it with three time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Price of Knowledge

Players have no maximum hand size.
At the beginning of each opponent's upkeep, Price of Knowledge deals damage to that player equal to the number of cards in that player's hand.

Venser's Journal

You have no maximum hand size.
At the beginning of your upkeep, you gain 1 life for each card in your hand.

Fate Unraveler

Whenever an opponent draws a card, Fate Unraveler deals 1 damage to that player.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Overbeing of Myth

Overbeing of Myth's power and toughness are each equal to the number of cards in your hand.
At the beginning of your draw step, draw an additional card.

Kami of the Crescent Moon

At the beginning of each player's draw step, that player draws an additional card.

Tales of the Ancestors

Each player with fewer cards in hand than the player with the most cards in hand draws cards equal to the difference.
Foretell {1}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Howling Mine

At the beginning of each player's draw step, if Howling Mine is untapped, that player draws an additional card.

Evolving Wilds

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

Mountain

Minds Aglow

Join forces — Starting with you, each player may pay any amount of mana. Each player draws X cards, where X is the total amount of mana paid this way.

Horn of Greed

Whenever a player plays a land, that player draws a card.

Vislor Turlough

Deal with the Black Guardian — When Vislor Turlough enters, you may have an opponent gain control of it. If you do, it's goaded for as long as they control it.
At the beginning of your end step, draw a card, then you lose life equal to the number of cards in your hand.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Realm Seekers

Realm Seekers enters with X +1/+1 counters on it, where X is the total number of cards in all players' hands.
{2}{G}, Remove a +1/+1 counter from Realm Seekers: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Wolfcaller's Howl

At the beginning of your upkeep, create X 2/2 green Wolf creature tokens, where X is the number of your opponents with four or more cards in hand.