Gríma Wormtongue

Your opponents can't gain life.
{T}, Sacrifice another creature: Target player loses 1 life. If the sacrificed creature was legendary, amass Orcs 2.

Giant Cindermaw

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Players can't gain life.

Knight of Dusk's Shadow

Menace (This creature can't be blocked except by two or more creatures.)
Your opponents can't gain life.
{1}{B}: This creature gets +1/+1 until end of turn.

Leyline of Punishment

If this card is in your opening hand, you may begin the game with it on the battlefield.
Players can't gain life.
Damage can't be prevented.

Witch Hunt

Players can't gain life.
At the beginning of your upkeep, this enchantment deals 4 damage to you.
At the beginning of your end step, target opponent chosen at random gains control of this enchantment.

The Lord of Pain

Menace
Your opponents can't gain life.
Whenever a player casts their first spell each turn, choose another target player. The Lord of Pain deals damage equal to that spell's mana value to the chosen player.

Sunspine Lynx

Players can't gain life.
Damage can't be prevented.
When this creature enters, it deals damage to each player equal to the number of nonbasic lands that player controls.

Havoc Festival

Players can't gain life.
At the beginning of each player's upkeep, that player loses half their life, rounded up.

Archfiend of Despair

Flying
Your opponents can't gain life.
At the beginning of each end step, each opponent loses life equal to the life that player lost this turn. (Damage causes loss of life.)

Quakebringer

Your opponents can't gain life.
At the beginning of your upkeep, Quakebringer deals 2 damage to each opponent. This ability triggers only if Quakebringer is on the battlefield or if Quakebringer is in your graveyard and you control a Giant.
Foretell {2}{R}{R}

Forsaken Wastes

Players can't gain life.
At the beginning of each player's upkeep, that player loses 1 life.
Whenever this enchantment becomes the target of a spell, that spell's controller loses 5 life.

Tibalt, Rakish Instigator

Your opponents can't gain life.
−2: Create a 1/1 red Devil creature token with "When this token dies, it deals 1 damage to any target."

Rampaging Ferocidon

Menace
Players can't gain life.
Whenever another creature enters, this creature deals 1 damage to that creature's controller.

Erebos, God of the Dead

Indestructible
As long as your devotion to black is less than five, Erebos isn't a creature. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
Your opponents can't gain life.
{1}{B}, Pay 2 life: Draw a card.

Everlasting Torment

Players can't gain life.
Damage can't be prevented.
All damage is dealt as though its source had wither. (A source with wither deals damage to creatures in the form of -1/-1 counters.)