Horrifying Revelation

Target player discards a card, then mills a card.

Plague Witch

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

Bog Witch

Psychic Miasma

Target player discards a card. If a land card is discarded this way, return Psychic Miasma to its owner's hand.

Heartless Pillage

Target opponent discards two cards.
Raid — If you attacked this turn, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Funeral Charm

Choose one —
• Target player discards a card.
• Target creature gets +2/-1 until end of turn.
• Target creature gains swampwalk until end of turn. (It can't be blocked as long as defending player controls a Swamp.)

Kaito's Pursuit

Target player discards two cards. Ninjas and Rogues you control gain menace until end of turn. (They can't be blocked except by two or more creatures.)

Divest

Target player reveals their hand. You choose an artifact or creature card from it. That player discards that card.

Harvest Fear

Target opponent discards two cards. (Then exile this card. You may cast the creature later from exile.)

Reaper of Night

Whenever Reaper of Night attacks, if defending player has two or fewer cards in hand, it gains flying until end of turn.

Reaper of Night // Harvest Fear

Okiba-Gang Shinobi

Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Okiba-Gang Shinobi deals combat damage to a player, that player discards two cards.

Strands of Undeath

Enchant creature
When Strands of Undeath enters, target player discards two cards.
{B}: Regenerate enchanted creature.

Mind Burst

Target player discards X cards, where X is one plus the number of cards named Mind Burst in all graveyards.

Cry of Contrition

Target player discards a card.
Haunt (When this spell card is put into a graveyard after resolving, exile it haunting target creature.)
When the creature Cry of Contrition haunts dies, target player discards a card.