Ancient Excavation

Draw cards equal to the number of cards in your hand, then discard a card for each card drawn this way.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Olivia's Dragoon

Discard a card: Olivia's Dragoon gains flying until end of turn.

Anvil of Bogardan

Players have no maximum hand size.
At the beginning of each player's draw step, that player draws an additional card, then discards a card.

Tasigur's Cruelty

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Each opponent discards two cards.

Apathy

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
At the beginning of the upkeep of enchanted creature's controller, that player may discard a card at random. If the player does, untap that creature.

Advanced Stitchwing

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

Tasigur, the Golden Fang

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
{2}{G/U}{G/U}: Mill two cards, then return a nonland card of an opponent's choice from your graveyard to your hand.

Cabal Initiate

Discard a card: Cabal Initiate gains lifelink until end of turn.
Threshold — Cabal Initiate gets +1/+2 as long as seven or more cards are in your graveyard.

Aquamoeba

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

Ancestral Reminiscence

Academy Wall

Defender
Whenever you cast an instant or sorcery spell, you may draw a card. If you do, discard a card. This ability triggers only once each turn.

Stitchwing Skaab

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

Aeromoeba

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

Ana Battlemage

Kicker {2}{U} and/or {1}{B} (You may pay an additional {2}{U} and/or {1}{B} as you cast this spell.)
When Ana Battlemage enters, if it was kicked with its {2}{U} kicker, target player discards three cards.
When Ana Battlemage enters, if it was kicked with its {1}{B} kicker, tap target untapped creature and that creature deals damage equal to its power to its controller.