Ruthless Sniper

Whenever you cycle or discard a card, you may pay {1}. If you do, put a -1/-1 counter on target creature.

Marsh Crocodile

When Marsh Crocodile enters the battlefield, return a blue or black creature you control to its owner's hand.
When Marsh Crocodile enters the battlefield, each player discards a card.

Oskar, Rubbish Reclaimer

This spell costs {1} less to cast for each different mana value among cards in your graveyard.
Whenever you discard a nonland card, you may cast it from your graveyard.

Sphinx's Tutelage

Whenever you draw a card, target opponent mills two cards. If two nonland cards that share a color were milled this way, repeat this process.
{5}{U}: Draw a card, then discard a card.

Mystic Redaction

At the beginning of your upkeep, scry 1.
Whenever you discard a card, each opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Bone Miser

Whenever you discard a creature card, create a 2/2 black Zombie creature token.
Whenever you discard a land card, add {B}{B}.
Whenever you discard a noncreature, nonland card, draw a card.

Stronghold Biologist

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

Feast of Sanity

Whenever you discard a card, Feast of Sanity deals 1 damage to any target and you gain 1 life.

Oppression

Whenever a player casts a spell, that player discards a card.

Hazoret's Monument

Red creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, you may discard a card. If you do, draw a card.

Archfiend of Ifnir

Flying
Whenever you cycle or discard another card, put a -1/-1 counter on each creature your opponents control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Tortured Existence

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

Murder of Crows

Flying
Whenever another creature dies, you may draw a card. If you do, discard a card.

Necromancer's Stockpile

{1}{B}, Discard a creature card: Draw a card. If the discarded card was a Zombie card, create a tapped 2/2 black Zombie creature token.

Zephyr Scribe

{U}, {T}: Draw a card, then discard a card.
Whenever you cast a noncreature spell, untap Zephyr Scribe.

Drake Haven

Whenever you cycle or discard a card, you may pay {1}. If you do, create a 2/2 blue Drake creature token with flying.

Undertaker

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

Megrim

Whenever an opponent discards a card, Megrim deals 2 damage to that player.

Mental Discipline

Tormod, the Desecrator

Whenever one or more cards leave your graveyard, create a tapped 2/2 black Zombie creature token.
Partner (You can have two commanders if both have partner.)

Zenith Seeker

Flying
Whenever you cycle or discard a card, target creature gains flying until end of turn.

Trial of Knowledge

When Trial of Knowledge enters the battlefield, draw three cards, then discard a card.
When a Cartouche enters the battlefield under your control, return Trial of Knowledge to its owner's hand.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

Raiders' Wake

Whenever an opponent discards a card, that player loses 2 life.
Raid — At the beginning of your end step, if you attacked this turn, target opponent discards a card.

Faith of the Devoted

Whenever you cycle or discard a card, you may pay {1}. If you do, each opponent loses 2 life and you gain 2 life.

Lazotep Chancellor

Whenever you discard a card, you may pay {1}. If you do, amass Zombies 2. (Put two +1/+1 counters on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

Dying to Serve

Whenever you discard one or more cards, create a tapped 2/2 black Zombie creature token. This ability triggers only once each turn.

Teferi's Tutelage

When Teferi's Tutelage enters the battlefield, draw a card, then discard a card.
Whenever you draw a card, target opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Waste Not

Whenever an opponent discards a creature card, create a 2/2 black Zombie creature token.
Whenever an opponent discards a land card, add {B}{B}.
Whenever an opponent discards a noncreature, nonland card, draw a card.

Compulsion

{1}{U}, Discard a card: Draw a card.
{1}{U}, Sacrifice Compulsion: Draw a card.

Containment Construct

Whenever you discard a card, you may exile that card from your graveyard. If you do, you may play that card this turn.

Curator of Mysteries

Flying
Whenever you cycle or discard another card, scry 1.
Cycling {U} ({U}, Discard this card: Draw a card.)

Sage of the Falls

Whenever Sage of the Falls or another non-Human creature enters the battlefield under your control, you may draw a card. If you do, discard a card.