Koskun Falls

At the beginning of your upkeep, sacrifice Koskun Falls unless you tap an untapped creature you control.
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Vona's Hunger

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Each opponent sacrifices a creature of their choice. If you have the city's blessing, instead each opponent sacrifices half the creatures they control of their choice, rounded up.

Endless Whispers

Each creature has "When this creature dies, choose target opponent. That player puts this card from its owner's graveyard onto the battlefield under their control at the beginning of the next end step."

Sanguine Bond

Whenever you gain life, target opponent loses that much life.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Gate to Phyrexia

Sacrifice a creature: Destroy target artifact. Activate only during your upkeep and only once each turn.

King Macar, the Gold-Cursed

Inspired — Whenever King Macar, the Gold-Cursed becomes untapped, you may exile target creature. If you do, create a Gold token. (It's an artifact with "Sacrifice this artifact: Add one mana of any color.")

Yawgmoth's Agenda

You can't cast more than one spell each turn.
You may play lands and cast spells from your graveyard.
If a card would be put into your graveyard from anywhere, exile it instead.

Nether Void

Whenever a player casts a spell, counter it unless that player pays {3}.

Horn of Greed

Whenever a player plays a land, that player draws a card.

Underworld Dreams

Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.

Maralen of the Mornsong

Players can't draw cards.
At the beginning of each player's draw step, that player loses 3 life, searches their library for a card, puts it into their hand, then shuffles.

Sol Ring

Necropotence

Skip your draw step.
Whenever you discard a card, exile that card from your graveyard.
Pay 1 life: Exile the top card of your library face down. Put that card into your hand at the beginning of your next end step.

Season of the Witch

At the beginning of your upkeep, sacrifice Season of the Witch unless you pay 2 life.
At the beginning of the end step, destroy all untapped creatures that didn't attack this turn, except for creatures that couldn't attack.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

Haunting Wind

Whenever an artifact becomes tapped or a player activates an artifact's ability without {T} in its activation cost, Haunting Wind deals 1 damage to that artifact's controller.

Diabolic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Demonic Tutor

Exquisite Blood

Whenever an opponent loses life, you gain that much life.

Mindslaver

{4}, {T}, Sacrifice Mindslaver: You control target player during that player's next turn. (You see all cards that player could see and make all decisions for the player.)

Bolas's Citadel

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.
{T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.

Hoarder's Greed

You lose 2 life and draw two cards, then clash with an opponent. If you win, repeat this process. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

Swamp

Phage the Untouchable

When Phage the Untouchable enters, if you didn't cast it from your hand, you lose the game.
Whenever Phage deals combat damage to a creature, destroy that creature. It can't be regenerated.
Whenever Phage deals combat damage to a player, that player loses the game.

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.