Stampede Driver

{1}{G}, {T}, Discard a card: Creatures you control get +1/+1 and gain trample until end of turn.

Goldmeadow Lookout

{W}, {T}, Discard a card: Create a 1/1 white Kithkin Soldier creature token named Goldmeadow Harrier. It has "{W}, {T}: Tap target creature."

Notorious Assassin

{2}{B}, {T}, Discard a card: Destroy target nonblack creature. It can't be regenerated.

Stronghold Biologist

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

Rushwood Herbalist

{G}, {T}, Discard a card: Regenerate target creature.

Waterfront Bouncer

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

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.

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.

Greel, Mind Raker

{X}{B}, {T}, Discard two cards: Target player discards X cards at random.

Bog Witch

Seismic Mage

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

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon, the Boundless enters the battlefield, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Deepwood Drummer

{G}, {T}, Discard a card: Target creature gets +2/+2 until end of turn.

Swamp

Balloon Peddler

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

Skirk Ridge Exhumer

{B}, {T}, Discard a card: Create a 1/1 black Zombie Goblin creature token named Festering Goblin. It has "When Festering Goblin dies, target creature gets -1/-1 until end of turn."

Icatian Crier

{1}{W}, {T}, Discard a card: Create two 1/1 white Citizen creature tokens.

Deepwood Elder

{X}{G}{G}, {T}, Discard a card: X target lands become Forests until end of turn.

Silverglade Pathfinder

{1}{G}, {T}, Discard a card: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Latulla, Keldon Overseer

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

Hammer Mage

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

Avenger en-Dal

{2}{W}, {T}, Discard a card: Exile target attacking creature. Its controller gains life equal to its toughness.

Kris Mage

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

Stronghold Machinist

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

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.

Undertaker

{B}, {T}, Discard a card: Return target creature card from your graveyard to your hand.

Llanowar Mentor

{G}, {T}, Discard a card: Create a 1/1 green Elf Druid creature token named Llanowar Elves. It has "{T}: Add {G}."

Mageta the Lion

{2}{W}{W}, {T}, Discard two cards: Destroy all creatures except for Mageta the Lion. Those creatures can't be regenerated.

Urborg Syphon-Mage

{2}{B}, {T}, Discard a card: Each other player loses 2 life. You gain life equal to the life lost this way.

Instigator

{1}{B}{B}, {T}, Discard a card: Creatures target player controls attack this turn if able.

Dawnstrider

{G}, {T}, Discard a card: Prevent all combat damage that would be dealt this turn.

Harvest Mage

{G}, {T}, Discard a card: Until end of turn, if you tap a land for mana, it produces one mana of a color of your choice instead of any other type and amount.

Plague Witch

{B}, {T}, Discard a card: Target creature gets -1/-1 until end of turn.

Divining Witch

{1}{B}, {T}, Discard a card: Choose a card name. Exile the top six cards of your library, then reveal cards from the top of your library until you reveal a card with the chosen name. Put that card into your hand and exile all other cards revealed this way.

Cackling Witch

{X}{B}, {T}, Discard a card: Target creature gets +X/+0 until end of turn.

Devout Witness

{1}{W}, {T}, Discard a card: Destroy target artifact or enchantment.

Arc Mage

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

Flowstone Channeler

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

Alexi, Zephyr Mage

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

Diplomatic Escort

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

Jolrael, Empress of Beasts

{2}{G}, {T}, Discard two cards: All lands target player controls become 3/3 creatures until end of turn. They're still lands.

Cho-Arrim Alchemist

{1}{W}{W}, {T}, Discard a card: The next time a source of your choice would deal damage to you this turn, prevent that damage. You gain life equal to the damage prevented this way.