Mishra's Factory

{T}: Add {C}.
{1}: This land becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Phyrexian Furnace

{T}: Exile the bottom card of target player's graveyard.
{1}, Sacrifice this artifact: Exile target card from a graveyard. Draw a card.

Engineered Plague

As this enchantment enters, choose a creature type.
All creatures of the chosen type get -1/-1.

Skittering Skirge

Flying
When you cast a creature spell, sacrifice this creature.

Swamp

Ravenous Rats

When this creature enters, target opponent discards a card.

Have

Dark Ritual

Phyrexian Negator

Trample
Whenever this creature is dealt damage, sacrifice that many permanents.

Hypnotic Specter

Flying
Whenever this creature deals damage to an opponent, that player discards a card at random.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Snuff Out

If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost.
Destroy target nonblack creature. It can't be regenerated.

Withered Wretch

Perish

Destroy all green creatures. They can't be regenerated.

Dystopia

Cumulative upkeep—Pay 1 life. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
At the beginning of each player's upkeep, that player sacrifices a green or white permanent of their choice.

Cursed Totem

Activated abilities of creatures can't be activated.

Cursed Scroll

{3}, {T}: Choose a card name, then reveal a card at random from your hand. If that card has the chosen name, Cursed Scroll deals 2 damage to any target.

Bottomless Pit

At the beginning of each player's upkeep, that player discards a card at random.

Smother

Destroy target creature with mana value 3 or less. It can't be regenerated.

The Rack

As this artifact enters, choose an opponent.
At the beginning of the chosen player's upkeep, this artifact deals X damage to that player, where X is 3 minus the number of cards in their hand.

Cabal Therapy

Choose a nonland card name. Target player reveals their hand and discards all cards with that name.
Flashback—Sacrifice a creature. (You may cast this card from your graveyard for its flashback cost. Then exile it.)