Sower of Discord

Flying
As Sower of Discord enters the battlefield, choose two players.
Whenever damage is dealt to one of the chosen players, the other chosen player also loses that much life.

Aether Flash

Whenever a creature enters the battlefield, Aether Flash deals 2 damage to it.

Hallow

Prevent all damage target spell would deal this turn. You gain life equal to the damage prevented this way.

Volcano Hellion

Volcano Hellion has echo {X}, where X is your life total. (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Volcano Hellion enters the battlefield, it deals an amount of damage of your choice to you and target creature. The damage can't be prevented.

Swans of Bryn Argoll

Flying
If a source would deal damage to Swans of Bryn Argoll, prevent that damage. The source's controller draws cards equal to the damage prevented this way.

Manabarbs

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.

Brash Taunter

Indestructible
Whenever Brash Taunter is dealt damage, it deals that much damage to target opponent.
{2}{R}, {T}: Brash Taunter fights another target creature.

Breena, the Demagogue

Flying
Whenever a player attacks one of your opponents, if that opponent has more life than another of your opponents, that attacking player draws a card and you put two +1/+1 counters on a creature you control.

Jade Monolith

{1}: The next time a source of your choice would deal damage to target creature this turn, that source deals that damage to you instead.

Pyrohemia

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pyrohemia.
{R}: Pyrohemia deals 1 damage to each creature and each player.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Rite of Passage

Whenever a creature you control is dealt damage, put a +1/+1 counter on it. (It must survive the damage to get the counter.)

Crypt Rats

{X}: Crypt Rats deals X damage to each creature and each player. Spend only black mana on X.

Pariah's Shield

All damage that would be dealt to you is dealt to equipped creature instead.
Equip {3}

Willowdusk, Essence Seer

{1}, {T}: Choose another target creature. Put a number of +1/+1 counters on it equal to the amount of life you gained this turn or the amount of life you lost this turn, whichever is greater. Activate only as a sorcery.

Neheb, the Eternal

Afflict 3 (Whenever this creature becomes blocked, defending player loses 3 life.)
At the beginning of your postcombat main phase, add {R} for each 1 life your opponents have lost this turn.

Darien, King of Kjeldor

Whenever you're dealt damage, you may create that many 1/1 white Soldier creature tokens.

Saskia the Unyielding

Vigilance, haste
As Saskia the Unyielding enters the battlefield, choose a player.
Whenever a creature you control deals combat damage to a player, it deals that much damage to the chosen player.

Vigor

Trample
If damage would be dealt to another creature you control, prevent that damage. Put a +1/+1 counter on that creature for each 1 damage prevented this way.
When Vigor is put into a graveyard from anywhere, shuffle it into its owner's library.

Stuffy Doll

Indestructible
As Stuffy Doll enters the battlefield, choose a player.
Whenever Stuffy Doll is dealt damage, it deals that much damage to the chosen player.
{T}: Stuffy Doll deals 1 damage to itself.

Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Conductor of Cacophony

Conductor of Cacophony enters the battlefield with two +1/+1 counters on it.
{B}, Remove a +1/+1 counter from Conductor of Cacophony: It deals 1 damage to each other creature and each player.

Kediss, Emberclaw Familiar

Whenever a commander you control deals combat damage to an opponent, it deals that much damage to each other opponent.
Partner (You can have two commanders if both have partner.)

Karma

At the beginning of each player's upkeep, Karma deals damage to that player equal to the number of Swamps they control.

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pestilence.
{B}: Pestilence deals 1 damage to each creature and each player.