Crown of Doom

Whenever a creature attacks you or a planeswalker you control, it gets +2/+0 until end of turn.
{2}: Target player other than Crown of Doom's owner gains control of it. Activate only during your turn.

Contested War Zone

Whenever a creature deals combat damage to you, that creature's controller gains control of Contested War Zone.
{T}: Add {C}.
{1}, {T}: Attacking creatures get +1/+0 until end of turn.

Demonic Pact

At the beginning of your upkeep, choose one that hasn't been chosen —
• This enchantment deals 4 damage to any target and you gain 4 life.
• Target opponent discards two cards.
• Draw two cards.
• You lose the game.

Jet Medallion

Black spells you cast cost {1} less to cast.

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.

Sol Ring

Ruby Medallion

Red spells you cast cost {1} less to cast.

Trove of Temptation

Each opponent must attack you or a planeswalker you control with at least one creature each combat if able.
At the beginning of your end step, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Pendant of Prosperity

Pendant of Prosperity enters under the control of an opponent of your choice.
{2}, {T}: Draw a card, then you may put a land card from your hand onto the battlefield. Pendant of Prosperity's owner draws a card, then that player may put a land card from their hand onto the battlefield.

Blim, Comedic Genius

Flying
Whenever Blim, Comedic Genius deals combat damage to a player, that player gains control of target permanent you control. Then each player loses life and discards cards equal to the number of permanents they control but don't own.

Risky Move

At the beginning of each player's upkeep, that player gains control of Risky Move.
When you gain control of Risky Move from another player, choose a creature you control and an opponent. Flip a coin. If you lose the flip, that opponent gains control of that creature.

Descent into Avernus

At the beginning of your upkeep, put two descent counters on Descent into Avernus. Then each player creates X Treasure tokens and Descent into Avernus deals X damage to each player, where X is the number of descent counters on Descent into Avernus.