Discard

Discard is an evergreen keyword action which takes cards from a player's hand and puts them in their graveyard.

Description
Discard is primarily in the black part of the color pie. Discard spells are more often at sorcery speed, a few have been printed at instant speed. The target of a discard spell more often gets to choose which cards to discard. Cards which give the choice to the discard spell's caster cost more, as do cards which force a random discard. Random discard spells are said to be "unfun", so fewer of them have been made. The Specters are famous for causing players to discard cards when they are unblocked. Black discard spells generally invoke a flavor of insanity or trauma, whereas red discard spells invoke one of fate or fire and blue discard spells invoke one of stealing.

For Odyssey, Mark Rosewater designed discard spells to challenge to mess around with the concept of card advantage and create threshold. In hindsight, it was an "interesting" idea but not "fun" to play.

Discard as a cost is primary in black, and secondary in red.

One card

 * Dismal Failure  their choice and counter spell
 * Frightful Delusion  their choice. Also counter spell unless they pay
 * Funeral Charm  their choice
 * Piracy Charm  their choice
 * Venarian Glimmer  your choice of nonland card with mana value  or less.

Two cards

 * Esper Charm  their choice - tri-modal spell
 * Haunting Hymn  their choice - If played during your main phase, then they discard four cards.

Variable cards

 * Tsabo's Decree  choose a creature type, target player discards all creature cards of the chosen type and also destroy all creatures of that type that player controls.

One card

 * Addle</c>  choose a color, your choice of card of that color
 * Assassin's Strike</c>  their choice and destroy target creature
 * Blackmail</c>  they reveal three cards, you choose one and that card is discarded.
 * Brain Pry</c>  name a nonland card, if its in that player's hand they discard a card with that name. If they can't, you draw a card.
 * Brainbite</c>  your choice + draw a card
 * Coercion</c>  your choice
 * Cry of Contrition</c>  their choice - Cry of Contrition has haunt, when the creature it haunts is put into a graveyard, target player discards a card.
 * Desecrated Earth</c>  their choice + destroy one of their lands
 * Despise</c>  your choice of creature or planeswalker card
 * Distress</c>  nonland card of your choice
 * Divest</c>  your choice of creature or artifact card
 * Duress</c>  nonland-noncreature card of your choice
 * Encroach</c>  nonbasic land of your choice
 * Flay</c>  randomly - unless they pay, they discard another card randomly
 * Horrifying Revelation</c>  their choice & they mill their top card of their library
 * Humiliate</c>  non-land of your choice.
 * <c>Hypnotic Cloud</c>  their choice - If kicker cost of  is paid then they discard three cards instead.
 * <c>Inquisition of Kozilek</c>  your choice of nonland card with mana value  or less
 * <c>Mental Vapors</c>  their choice - Cipher
 * <c>Mind Knives</c>  randomly
 * <c>Mind Peel</c>  their choice - Buyback
 * <c>Mind Ravel</c>  their choice - Slowtrip
 * <c>Mire's Toll</c>  your choice of 1 of X cards revealed from their hand where X is the number of swamps you control
 * <c>Nightmare Void</c>  your choice - Dredge 2
 * <c>Ostracize</c>  your choice of a creature
 * <c>Pain (Pain/Suffering)</c>  their choice
 * <c>Psychic Miasma</c>  their choice, if its a land, return this card to your hand.
 * <c>Psychic Spear</c>  your choice of a Spirit or Arcane card
 * <c>Pulling Teeth</c>  their choice - Clash if you win, then two cards instead.
 * <c>Pulse of the Dross</c>  they reveal three cards, you choose one of those cards. If that player has more cards in hand than you, return Pulse of the Dross to its owner's hand.
 * <c>Raven's Crime</c>  their choice - Retrace
 * <c>Resounding Scream</c>  their choice or two cards if cycled for.
 * <c>River's Grasp</c>  your choice of a nonland card if  was spent to play River's Grasp.
 * <c>Shattered Dreams</c>  artifact card of your choice
 * <c>Skull Fracture</c>  - Flashback
 * <c>Smallpox</c>  each player loses 1 life, discards 1 card, sacrifices 1 creature and 1 land.
 * <c>Specter's Wail</c>  randomly
 * <c>Strongarm Tactics</c>  each player discards a card, then each player who didn't discard a creature card this way loses 4 life.
 * <c>Surging Dementia</c>  their choice - Ripple 4
 * <c>Syphon Mind</c>  each other player discards a card and you draw a card for each card discarded this way.
 * <c>Talara's Bane</c>  your choice of green or white creature card and you gain life equal to that creature card's toughness.
 * <c>Thoughtseize</c>  your choice of nonland card and you lose 2 life
 * <c>Unhinge</c>  their choice - Cantrip
 * <c>Unmask</c>  your choice of nonland card - (alternate casting cost of removing a black card in your hand from the game)

Two cards

 * <c>Blightning</c>  their choice and deals 3 damage.
 * <c>Bog Down</c>  their choice - If kicker cost of sacrificing a land is paid then they discard three cards instead.
 * <c>Chain of Smog</c>  their choice - that player may copy this spell and may choose a new target for that copy.
 * <c>Consult the Necrosages</c>  their choice
 * <c>Deception</c>  their choice
 * <c>Down (Down/Dirty)</c>  their choice
 * <c>Extortion</c>  your choice
 * <c>Fill with Fright</c>  their choice - Scry 2
 * <c>Gerrard's Verdict</c>  their choice and you gain 3 life for each land card discarded this way.
 * <c>Gruesome Discovery</c>  their choice - If morbid your choice
 * <c>Hymn to Tourach</c>  randomly
 * <c>Mental Agony</c>  their choice and loses 2 life
 * <c>Mind Rot</c>  their choice
 * <c>Mindculling</c>  you draw 2 cards and they discard 2 cards their choice
 * <c>Noggin Whack</c>  they reveal three cards, you choose two of those cards.
 * <c>Probe</c>  If kicker cost of  is paid then their choice
 * <c>Purge the Profane</c>  their choice and you gain 2 life
 * <c>Skull Rend</c>  - deals 2 damage to each opponent and they discard 2 cards at random
 * <c>Skullscorch</c>  randomly unless deals 4 damage
 * <c>Splitting Headache</c>  Choose - they discard two of their choice, or they discard one of your choice
 * <c>Stupor</c>  one randomly, one their choice
 * <c>Tendrils of Despair</c>  & sacrifice a creature; their choice
 * <c>Tourach's Canticle</c>  you choose one and one at random.
 * <c>Unburden</c>  their choice - Cycling
 * <c>Unnerve</c>  each opponent, their choice
 * <c>Waking Nightmare</c>  their choice - Arcane
 * <c>Wrench Mind</c>  their choice of two cards unless they discard an artifact card

Three cards

 * <c>Burning Inquiry</c>  - each player draws three cards, then discards three cards at random.
 * <c>Cruel Ultimatum</c>  - their choice and they sacrifice a creature and lose 5 life while the caster returns a creature from their graveyard to their hand, draws three cards then gains 5 life.
 * <c>Delirium Skeins</c>  each player
 * <c>Fugue</c>  their choice
 * <c>Mindstab</c>  their choice - Suspend 4 -
 * <c>Three Tragedies</c>  their choice - Arcane

Variable cards

 * <c>Abandon Hope</c>  & discard X cards; your choice of X cards
 * <c>Amnesia</c>  your choice of all nonland cards
 * <c>Cabal Conditioning</c>  any number of players each discards cards from their hand equal to the highest mana value among permanents you control.
 * <c>Cabal Therapy</c>  name a nonland card, target player discards all cards with that name. Also has flashback (sacrifice a creature).
 * <c>Death Cloud</c>  each player loses X life, discards X cards, sacrifices X creatures and X lands.
 * <c>Fall (Rise/Fall)</c>  target player reveals two cards at random, then discards each nonland card revealed this way.
 * <c>Hint of Insanity</c>  all nonland cards with the same name as another card in their hand
 * <c>Ill-Gotten Gains</c>  exile this card, each player discards their hand then puts up to three cards from their graveyard into their hand.
 * <c>Last Rites</c>  you discard any number of cards from your hand, then you choose a nonland card for each card to discard of target player.
 * <c>Mind Burst</c>  their choice of X cards where X is one plus the number of Mind Burst cards in all graveyards.
 * <c>Mind Extraction</c>  you sacrifice a creature, target player reveals their hand and discards all cards of each of the sacrificed creatures colors.
 * <c>Mind Shatter</c>  X cards at random
 * <c>Mind Sludge</c>  target player discards a card from their hand for each swamp you control.
 * <c>Mind Twist</c>  randomly discard X cards
 * <c>Mind Warp</c>  your choice of X cards
 * <c>Monomania</c>  target player chooses a card from their hand and discards the rest.
 * <c>Noxious Vapors</c>  each player reveals their cards and choose one card of each color, then discards all other nonland cards
 * <c>Persecute</c>  choose a color, target player discards all cards of the chosen color.
 * <c>Pox</c>  each player loses 1/3 of their life, discards 1/3 of their cards, sacrifices 1/3 of their creatures and 1/3 of their lands. Round each loss up.
 * <c>Rakdos's Return</c>  - target opponent discards X cards and deals X damage to them
 * <c>Sink into Takenuma</c>  sweep - return any number of swamps you control to their owner's hand, target player discards a card for each swamp returned this way.
 * <c>Trapfinder's Trick</c>  target player discards all Trap cards.
 * <c>Tyrannize</c>  they discard their hand unless they pay 7 life.
 * <c>Voices from the Void</c>  domain - on caster's lands, their choice.
 * <c>Void</c>  choose a number, destroy all artifacts and creatures with converted mana cost equal to that number. Then target player discards all nonland cards with converted mana cost equal to the number.
 * <c>Wistful Thinking</c>  they draw two cards, then discard (up to) four cards, their choice.
 * <c>Wit's End</c>  target player discards their hand

Planeswalkers which cause discard

 * <c>Chandra Ablaze</c>  - Remove 2 loyalty counters, all players discard hand, then draw 3 cards
 * <c>Liliana of the Veil</c>  - +1 loyalty counter, each player
 * <c>Liliana Vess</c>  - +1 loyalty counter, their choice
 * <c>Nicol Bolas, Planeswalker</c>  - -9 loyalty counters, their choice seven cards (also deals 7 damage)

Creatures which cause discard

 * <c>Bala Ged Thief</c>  - one your choice pulled from a set of X cards in their hand where X is the number of Ally creatures you control
 * <c>Bloodhusk Ritualist</c>  - their choice for each time it was kicked. Multikicker
 * <c>Cinderhaze Wretch</c>  - undefined: Their choice, only during your turn.
 * <c>Noggle Ransacker</c>  - when this comes into play, each player draws two cards then discards a card at random.
 * <c>Rakdos Ringleader</c>  - when this deals combat damage, one card at random
 * <c>Riptide Pilferer</c>  - their choice, also has morph
 * <c>Scandalmonger</c>  -  target player discards a card, their choice. Any player may play this ability when they could play a sorcery.
 * <c>Slavering Nulls</c>  - if it deals damage to a player and you control a swamp, their choice

Legends
There are two Legends, which are creatures with the legendary supertype, that cause an opponent to discard.
 * <c>Gwendlyn Di Corci</c>  - undefined: target player discards one card from his or her hand at random, this power can only be used during your turn.
 * <c>Nicol Bolas</c>  - Whenever Nicol Bolas deals damage to an opponent, that player discards his or her hand.

Rats
Some rats cause discard to their opponents and mostly when they enter the battlefield, some rats force discard when combat damage occurs.
 * <c>Drainpipe Vermin</c>  - when this dies, if  is paid, then target player discards a card, their choice.
 * <c>Earsplitting Rats</c>  - when this enters the battlefield, each player discards a card, their choice
 * <c>Hellhole Rats</c>   - when this enters the battlefield, target player discards a card, their choice
 * <c>Nezumi Bone-Reader</c>  -, sacrifice a creature, target player discards a card (activate this ability only any time you could play a sorcery), their choice
 * <c>Nezumi Shortfang</c>  -, undefined target opponent discards a card, their choice, then if that player has no cards in hand, flip Nezumi Shortfang
 * <c>Okiba-Gang Shinobi</c>  - when this deals combat damage to a player, that player discards two cards, their choice
 * <c>Ravenous Rats</c>  - when this enters the battlefield, target opponent discards a card, their choice
 * <c>Rotting Rats</c>  - when this enters the battlefield, each player discards a card, their choice
 * <c>Sanity Gnawers</c>  - when this enters the battlefield, target player discards a card at random
 * <c>Stronghold Rats</c>  - when this deals combat damage to a player, each player discards a card, their choice

Specters
Specters are flying creatures and the most famous for causing opponents to discard when they aren't blocked.
 * <c>Abyssal Specter</c>  2/3 - their choice
 * <c>Blazing Specter</c>  2/2 - their choice, also has haste
 * <c>Blizzard Specter</c>  2/3 - their choice or force them to return a permanent they control to its owner's hand
 * <c>Doomsday Specter</c>  2/3 - your choice, also has gating
 * <c>Entropic Specter</c>  */* - their choice, has power / toughness equal to the number of cards in target opponent's hand
 * <c>Guul Draz Specter</c>  2/2 - their choice
 * <c>Hollow Specter</c>  2/2 - pay, that player reveals X cards from their hand, you choose one of those revealed.
 * <c>Hypnotic Specter</c>  2/2 - randomly
 * <c>Liliana's Specter</c>  2/1 - (only when this enters the battlefield) their choice
 * <c>Needle Specter</c>  1/1 - their choice (discards that many cards equal to the number of combat damage)
 * <c>Scythe Specter</c>  4/4 - their choice and each of them who discarded a card with the highest converted mana cost among cards discarded this way loses life equal to that converted mana cost.
 * <c>Sedraxis Specter</c>  3/2 - their choice, also has unearth
 * <c>Shrieking Specter</c>  2/2 - their choice, whenever Shrieking Specter attacks
 * <c>Shimian Specter</c>  2/2 - nonland, your choice, removes all cards with same name from hand, library, graveyard
 * <c>Silent Specter</c>  4/4 - two cards their choice
 * <c>Tainted Specter</c>  2/2 - (only for activated ability) their choice unless they mill their top card of their library and deals 1 damage to each creature and each player.
 * <c>Whispering Specter</c>  1/1 - sacrifice it instead, target player discards a card for each poison counter they have.

Enchantments which cause discard

 * <c>Bereavement</c>  - whenever a green creature dies, its controller discards a card.
 * <c>Bottomless Pit</c>  - at the beginning of each player's upkeep, that player discards a card at random.
 * <c>Brink of Madness</c>  - at the beginning of your upkeep, if you have no cards in hand, sacrifice Brink of Madness and target opponent discards his or her hand.
 * <c>Cabal Shrine</c>  - whenever a player casts a spell, that player discards X cards, where X is the number of cards in all graveyards with the same name as that spell.
 * <c>Dire Undercurrents</c>  - whenever a black creature enters the battlefield under your control, you may have target player discard a card.
 * <c>Discordant Dirge</c>  - at the beginning of your upkeep, you may put a verse counter on Discordant Dirge.  and sacrifice Discordant Dirge: Look at target opponent's hand and choose up to X cards from it, where X is the number of verse counters on Discordant Dirge. That player discards those cards.
 * <c>Gibbering Descent</c>  - at the beginning of each player's upkeep, that player loses 1 life and discards a card. Hellbent - Skip your upkeep step if you have no cards in hand. Madness
 * <c>Honden of Night's Reach</c>  - at the beginning of your upkeep, target opponent discards a card for each Shrine you control.
 * <c>Larceny</c>  - whenever a creature you control deals combat damage to a player, that player discards a card.
 * <c>Leshrac's Sigil</c>  - whenever an opponent casts a green spell, you may pay . If you do, look at that player's hand and choose a card from it. The player discards that card.
 * <c>Mind Slash</c>  -  and sacrifice a creature: Target opponent reveals his or her hand. You choose a card from it. That player discards that card.
 * <c>Necrogen Mists</c>  - at the beginning of each player's upkeep, that player discards a card.
 * <c>Oppression</c>  - whenever a player casts a spell, that player discards a card.
 * <c>Putrefaction</c>  - whenever a player casts a green or white spell, that player discards a card.
 * <c>Seer's Vision</c>  - your opponents play with their hands revealed. Sacrifice Seer's Vision: Look at target player's hand and choose a card from it. That player discards that card.
 * <c>Triumph of Cruelty</c>  - at the beginning of your upkeep, target opponent discards a card if you control the creature with the greatest power or tied for the greatest power.
 * <c>Warped Devotion</c>  - whenever a permanent is returned to a player's hand, that player discards a card.

Auras

 * <c>Dying Wail</c>  - when enchanted creature dies, two cards their choice
 * <c>Strands of Undeath</c>  - when this enters the battlefield, two cards, their choice

The following auras enchanted on creatures cause opponents to discard when they aren't blocked.
 * <c>Cloak of Confusion</c>  - prevent combat damage to force discard of one card, random
 * <c>Elder Mastery</c>  - two cards their choice
 * <c>Helm of the Ghastlord</c>  - if enchanted creature is black, one card, their choice

Artifacts which cause discard

 * <c>Disrupting Scepter</c>  -, undefined - their choice
 * <c>Necrogen Spellbomb</c>  -, Sacrifice this - their choice
 * <c>Scepter of Fugue</c>  - ,undefined - their choice
 * <c>Scroll of Griselbrand</c>  -, Sacrifice this - their choice and if you control a Demon, that player also loses 3 life
 * <c>Shrine of Limitless Power</c>  - at the beginning of your upkeep or whenever you cast a black spell, put a charge counter on Shrine of Limitless Power. ,undefined, Sacrifice this - their choice for each charge counter on it.

Equipment

 * <c>Specter's Shroud</c>  - Equip  - if a player is damaged by a creature equipped with this, their choice. The name Specter's Shroud is an homage to the numerous Specter creatures that cause discard if they attack and are unblocked.
 * <c>Sword of Feast and Famine</c>  - Equip  - if a player is damaged by a creature equipped with this, their choice.