Circular Logic

Counter target spell unless its controller pays {1} for each card in your graveyard.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

All-Seeing Arbiter

Flying
Whenever All-Seeing Arbiter enters or attacks, draw two cards, then discard a card.
Whenever you discard a card, target creature an opponent controls gets -X/-0 until your next turn, where X is the number of different mana values among cards in your graveyard.

Stronghold Biologist

{U}{U}, {T}, Discard a card: Counter target creature spell.

Dreamscape Artist

{2}{U}, {T}, Discard a card, Sacrifice a land: Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Containment Construct

Whenever you discard a card, you may exile that card from your graveyard. If you do, you may play that card this turn.

Cloudseeder

Flying
{U}, {T}, Discard a card: Create a 1/1 blue Faerie creature token named Cloud Sprite. It has flying and "Cloud Sprite can block only creatures with flying."

Nagging Thoughts

Look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.
Madness {1}{U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Curator of Mysteries

Flying
Whenever you cycle or discard another card, scry 1.
Cycling {U} ({U}, Discard this card: Draw a card.)

Cephalid Inkshrouder

Discard a card: Cephalid Inkshrouder gains shroud until end of turn and can't be blocked this turn. (A creature with shroud can't be the target of spells or abilities.)

Breakthrough

Draw four cards, then choose X cards in your hand and discard the rest.

Kederekt Leviathan

When Kederekt Leviathan enters, return all other nonland permanents to their owners' hands.
Unearth {6}{U} ({6}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Thalakos Drifters

Discard a card: Thalakos Drifters gains shadow until end of turn. (It can block or be blocked by only creatures with shadow.)

Star Compass

Star Compass enters tapped.
{T}: Add one mana of any color that a basic land you control could produce.

Archive Haunt

Flying
Whenever Archive Haunt attacks, draw a card, then discard a card.
If Archive Haunt would be put into a graveyard from anywhere, exile it instead.

Overwhelmed Archivist

When Overwhelmed Archivist enters, draw a card, then discard a card.
Disturb {3}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Overwhelmed Archivist // Archive Haunt

Burnished Hart

{3}, Sacrifice Burnished Hart: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Bag of Holding

Whenever you discard a card, exile that card from your graveyard.
{2}, {T}: Draw a card, then discard a card.
{4}, {T}, Sacrifice Bag of Holding: Return all cards exiled with Bag of Holding to their owner's hand.

Zenith Seeker

Flying
Whenever you cycle or discard a card, target creature gains flying until end of turn.

Cephalid Broker

{T}: Target player draws two cards, then discards two cards.

Waterfront Bouncer

{U}, {T}, Discard a card: Return target creature to its owner's hand.

Sky Diamond

Mystic Redaction

At the beginning of your upkeep, scry 1.
Whenever you discard a card, each opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Aether Tide

As an additional cost to cast this spell, discard X creature cards.
Return X target creatures to their owners' hands.

Welcome to the Fold

Madness {X}{U}{U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)
Gain control of target creature if its toughness is 2 or less. If this spell's madness cost was paid, instead gain control of that creature if its toughness is X or less.

Aquamoeba

Discard a card: Switch Aquamoeba's power and toughness until end of turn.

Scampering Surveyor

When Scampering Surveyor enters, search your library for a basic land card or Cave card, put it onto the battlefield tapped, then shuffle.

Walking Atlas

{T}: You may put a land card from your hand onto the battlefield.

Merfolk Looter

Wharf Infiltrator

Skulk (This creature can't be blocked by creatures with greater power.)
Whenever Wharf Infiltrator deals combat damage to a player, you may draw a card. If you do, discard a card.
Whenever you discard a creature card, you may pay {2}. If you do, create a 3/2 colorless Eldrazi Horror creature token.

Chamber of Manipulation

Enchant land
Enchanted land has "{T}, Discard a card: Gain control of target creature until end of turn."

Gutter Shortcut

Enchant creature
Enchanted creature can't be blocked as long as it's attacking alone.
If Gutter Shortcut would be put into a graveyard from anywhere, exile it instead.

Gutter Skulker

Gutter Skulker can't be blocked as long as it's attacking alone.
Disturb {3}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Gutter Skulker // Gutter Shortcut

Thought Courier

Ominous Sphinx

Flying
Whenever you cycle or discard a card, target creature an opponent controls gets -2/-0 until end of turn.

Fellwar Stone

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

Catlike Curiosity

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
If Catlike Curiosity would be put into a graveyard from anywhere, exile it instead.

Mischievous Catgeist

Whenever Mischievous Catgeist deals combat damage to a player, draw a card.
Disturb {2}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Mischievous Catgeist // Catlike Curiosity

Commander's Sphere

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

Stronghold Machinist

{U}{U}, {T}, Discard a card: Counter target noncreature spell.

Oath of Scholars

At the beginning of each player's upkeep, that player chooses target player who has more cards in hand than they do and is their opponent. The first player may discard their hand and draw three cards.

Scuttletide

{1}, Discard a card: Create a 0/3 blue Crab creature token.
Delirium — Crabs you control get +1/+1 as long as there are four or more card types among cards in your graveyard.

Telekinetic Bonds

Whenever a player discards a card, you may pay {1}{U}. If you do, you may tap or untap target permanent.

Ghostly Pilferer

Whenever Ghostly Pilferer becomes untapped, you may pay {2}. If you do, draw a card.
Whenever an opponent casts a spell from anywhere other than their hand, draw a card.
Discard a card: Ghostly Pilferer can't be blocked this turn.

Drake Haven

Whenever you cycle or discard a card, you may pay {1}. If you do, create a 2/2 blue Drake creature token with flying.

Turbulent Dreams

As an additional cost to cast this spell, discard X cards.
Return X target nonland permanents to their owners' hands.

Cephalid Looter

{T}: Target player draws a card, then discards a card.

Hisoka, Minamo Sensei

{2}{U}, Discard a card: Counter target spell if it has the same mana value as the discarded card.

Stitchwing Skaab

Flying
{1}{U}, Discard two cards: Return Stitchwing Skaab from your graveyard to the battlefield tapped.

Trickster Mage

{U}, {T}, Discard a card: You may tap or untap target artifact, creature, or land.

Diplomatic Escort

{U}, {T}, Discard a card: Counter target spell or ability that targets a creature.

Iymrith, Desert Doom

Flying
Iymrith, Desert Doom has ward {4} as long as it's untapped.
Whenever Iymrith deals combat damage to a player, draw a card. Then if you have fewer than three cards in hand, draw cards equal to the difference.

Lore Broker

{T}: Each player draws a card, then discards a card.

Draconian Cylix

{2}, {T}, Discard a card at random: Regenerate target creature.

Tolarian Winds

Discard all the cards in your hand, then draw that many cards.

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.

Champion of Wits

When Champion of Wits enters, you may draw cards equal to its power. If you do, discard two cards.
Eternalize {5}{U}{U} ({5}{U}{U}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Snake Wizard with no mana cost. Eternalize only as a sorcery.)

Alexi, Zephyr Mage

{X}{U}, {T}, Discard two cards: Return X target creatures to their owners' hands.

Ghost of Ramirez DePietro

Ghost of Ramirez DePietro can't be blocked by creatures with toughness 3 or greater.
Whenever Ghost of Ramirez DePietro deals combat damage to a player, choose up to one target card in a graveyard that was discarded or put there from a library this turn. Put that card into its owner's hand.
Partner (You can have two commanders if both have partner.)

Obsessive Search

Draw a card.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Reckless Scholar

Island

Overtaker

{3}{U}, {T}, Discard a card: Untap target creature and gain control of it until end of turn. That creature gains haste until end of turn.

Cunning Survivor

Whenever you cycle or discard a card, Cunning Survivor gets +1/+0 until end of turn and can't be blocked this turn.

Rites of Refusal

Discard any number of cards. Counter target spell unless its controller pays {3} for each card discarded this way.

Advanced Stitchwing

Flying
{2}{U}, Discard two cards: Return Advanced Stitchwing from your graveyard to the battlefield tapped.