Farewell to Arms

As Farewell to Arms enters, choose a hand attached to an opponent's arm.
When the chosen hand isn't behind its owner's back, sacrifice Farewell to Arms. If you do, that player discards their hand . . . of cards. (The lawyers wouldn't let us do it the other way.)

Subcontract

A person outside the game looks at target opponent's hand and chooses a nonland card from it. That player discards that card.

Infernal Spawn of Evil

Flying, first strike
{1}{B}, Reveal Infernal Spawn of Evil from your hand, Say "It's coming!": Infernal Spawn of Evil deals 1 damage to target opponent or planeswalker. Activate only during your upkeep and only once each turn.

Phyrexian Librarian

Flying, trample
At the beginning of your upkeep, exile the top card of your library and balance it on your body.
When a balanced card falls or touches another balanced card, sacrifice Phyrexian Librarian.

Masterful Ninja

Haste
Reveal Masterful Ninja from your hand: Masterful Ninja is on the battlefield and in your hand until end of turn.
{1}{B}: Masterful Ninja gets +1/+1 until end of turn.

Whenever a creature deals damage to a player, that player may say "Ow" once for each permanent named Ow. If the player doesn't, Ow deals 1 damage to them.

Blacker Lotus

{T}: Tear Blacker Lotus into pieces. Add four mana of any one color. Remove the pieces from the game.

Volrath's Motion Sensor

Enchant player
As Volrath's Motion Sensor enters, choose one of enchanted player's hands. That player balances Volrath's Motion Sensor on the back of that hand.
When Volrath's Motion Sensor falls off the chosen hand, sacrifice Volrath's Motion Sensor and enchanted player loses 3 life.

Togglodyte

Togglodyte enters turned on.
Whenever a player casts a spell, toggle Togglodyte's ON/OFF switch.
As long as Togglodyte is turned off, it can't attack or block, and prevent all damage it would deal.

Necro-Impotence

Skip your untap step.
At the beginning of your upkeep, you may pay X life. If you do, untap X permanents.
Pay ½ life: Exile the top card of your library face down. Put that card into your hand at the beginning of the next end step.

Dark Ritual

Swamp

Hangman

As Hangman enters, secretly note a word with six to eight letters.
{1}: Target player who doesn't control Hangman guesses the noted word or an unguessed letter in that word. If they guess wrong, put a +1/+1 counter on Hangman. Any player may activate this ability.
When a player guesses the noted word or all of its letters, sacrifice Hangman.