Tolarian Sentinel

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

Flowstone Channeler

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

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."

Greel, Mind Raker

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

Zirda, the Dawnwaker

Companion — Each permanent card in your starting deck has an activated ability. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Abilities you activate that aren't mana abilities cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.
{1}, {T}: Target creature can't block this turn.

Icatian Crier

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

Latulla, Keldon Overseer

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

Undertaker

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

Stronghold Biologist

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

Jegantha, the Wellspring

Companion — No card in your starting deck has more than one of the same mana symbol in its mana cost. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
{T}: Add {W}{U}{B}{R}{G}. This mana can't be spent to pay generic mana costs.

Rushwood Herbalist

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

Waterfront Bouncer

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

Alexi, Zephyr Mage

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

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.

Devout Witness

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

Stronghold Machinist

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

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."

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon, the Boundless enters, 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.

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.

Sliversmith

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

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."

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

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.

Diplomatic Escort

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

Kris Mage

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

Greenseeker

{G}, {T}, Discard a card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.

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."

Notorious Assassin

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

Cackling Witch

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

Bog Witch

Dawnstrider

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

Trickster Mage

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