Sparkspitter

{R}, {T}, Discard a card: Create a 3/1 red Elemental creature token named Spark Elemental. It has trample, haste, and "At the beginning of the end step, sacrifice Spark Elemental."

Sliversmith

{1}, {T}, Discard a card: Create a 1/1 colorless Sliver artifact creature token named Metallic Sliver.

Anje's Ravager

Anje's Ravager attacks each combat if able.
Whenever Anje's Ravager attacks, discard your hand, then draw three cards.
Madness {1}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Diplomatic Escort

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

Jaya Ballard, Task Mage

{R}, {T}, Discard a card: Destroy target blue permanent.
{1}{R}, {T}, Discard a card: Jaya Ballard, Task Mage deals 3 damage to any target. A creature dealt damage this way can't be regenerated this turn.
{5}{R}{R}, {T}, Discard a card: Jaya Ballard deals 6 damage to each creature and each player.

Firefright Mage

{1}{R}, {T}, Discard a card: Target creature can't be blocked this turn except by artifact creatures and/or red creatures.

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.

Kris Mage

{R}, {T}, Discard a card: Kris Mage deals 1 damage to any target.

Alexi, Zephyr Mage

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

Change of Fortune

Discard your hand, then draw a card for each card you've discarded this turn.

Flowstone Channeler

{1}{R}, {T}, Discard a card: Target creature gets +1/-1 and gains haste until end of turn.

Bola Warrior

{R}, {T}, Discard a card: Target creature can't block this turn.

Latulla, Keldon Overseer

{X}{R}, {T}, Discard two cards: Latulla, Keldon Overseer deals X damage to any target.

Rielle, the Everwise

Rielle, the Everwise gets +1/+0 for each instant and sorcery card in your graveyard.
Whenever you discard one or more cards for the first time each turn, draw that many cards.

Trickster Mage

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

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.)

Arc Mage

{2}{R}, {T}, Discard a card: Arc Mage deals 2 damage divided as you choose among one or two targets.

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.)

Balloon Peddler

{U}, {T}, Discard a card: Target creature gains flying until end of turn.

Stronghold Machinist

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

Diamond Lion

{T}, Discard your hand, Sacrifice Diamond Lion: Add three mana of any one color. Activate only as an instant.

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.

Conflagrate

Conflagrate deals X damage divided as you choose among any number of targets.
Flashback—{R}{R}, Discard X cards. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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."

Blaster Mage

{R}, {T}, Discard a card: Destroy target Wall.

Avacyn's Judgment

Madness {X}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)
Avacyn's Judgment deals 2 damage divided as you choose among any number of targets. If this spell's madness cost was paid, it deals X damage divided as you choose among those permanents and/or players instead.

Hammer Mage

{X}{R}, {T}, Discard a card: Destroy all artifacts with mana value X or less.

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.)

Squee, Goblin Nabob

At the beginning of your upkeep, you may return Squee, Goblin Nabob from your graveyard to your hand.

Stronghold Biologist

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

Kyren Flamewright

{2}{R}, {T}, Discard a card: Create two 1/1 blue and red Elemental creature tokens. Creatures you control get +1/+0 and gain haste until end of turn.

Invasion of Mercadia

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Mercadia enters, you may discard a card. If you do, draw two cards.

Invasion of Mercadia // Kyren Flamewright

Tolarian Sentinel

Flying
{U}, {T}, Discard a card: Return target permanent you control to its owner's hand.