Forbidden Orchard

{T}: Add one mana of any color.
Whenever you tap Forbidden Orchard for mana, target opponent creates a 1/1 colorless Spirit creature token.

Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek the Merciless deals damage equal to that spell's mana value to any target.

Duskwielder

Boast — {1}: Target opponent loses 1 life and you gain 1 life. (Activate only if this creature attacked this turn and only once each turn.)

Covetous Urge

Target opponent reveals their hand. You choose a nonland card from that player's graveyard or hand and exile it. You may cast that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.

Xanathar, Guild Kingpin

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Fires of Mount Doom

When Fires of Mount Doom enters, it deals 2 damage to target creature an opponent controls. Destroy all Equipment attached to that creature.
{2}{R}: Exile the top card of your library. You may play that card this turn. When you play a card this way, Fires of Mount Doom deals 2 damage to each player.

Nihilistic Glee

{2}{B}, Discard a card: Target opponent loses 1 life and you gain 1 life.
Hellbent — {1}, Pay 2 life: Draw a card. Activate only if you have no cards in hand.

Corpse Traders

{2}{B}, Sacrifice a creature: Target opponent reveals their hand. You choose a card from it. That player discards that card. Activate only as a sorcery.

Custody Battle

Enchant creature
Enchanted creature has "At the beginning of your upkeep, target opponent gains control of this creature unless you sacrifice a land."

Murder

Blatant Thievery

For each opponent, gain control of target permanent that player controls.

Desecrate Reality

For each opponent, exile up to one target permanent that player controls with an even mana value. (Zero is even.)
Adamant — If at least three colorless mana was spent to cast this spell, return a permanent card with an odd mana value from your graveyard to the battlefield.

See Double

This spell can't be copied.
Choose one. If an opponent has eight or more cards in their graveyard, you may choose both instead.
• Copy target spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)
• Create a token that's a copy of target creature.

Lost Vale

(Transforms from Dowsing Dagger.)
{T}: Add three mana of any one color.

Dowsing Dagger

When Dowsing Dagger enters, target opponent creates two 0/2 green Plant creature tokens with defender.
Equipped creature gets +2/+1.
Whenever equipped creature deals combat damage to a player, you may transform Dowsing Dagger.
Equip {2}

Dowsing Dagger // Lost Vale

Sorcerous Sight

Look at target opponent's hand.
Draw a card.

Marchesa, Dealer of Death

Whenever you commit a crime, you may pay {1}. If you do, look at the top two cards of your library. Put one of them into your hand and the other into your graveyard. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Demolition Field

{T}: Add {C}.
{2}, {T}, Sacrifice this land: Destroy target nonbasic land an opponent controls. That land's controller may search their library for a basic land card, put it onto the battlefield, then shuffle. You may search your library for a basic land card, put it onto the battlefield, then shuffle.

Training Grounds

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.