Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Morality Shift

Exchange your graveyard and library. Then shuffle your library.

Syr Konrad, the Grim

Whenever another creature dies, or a creature card is put into a graveyard from anywhere other than the battlefield, or a creature card leaves your graveyard, Syr Konrad deals 1 damage to each opponent.
{1}{B}: Each player mills a card. (They each put the top card of their library into their graveyard.)

Gray Merchant of Asphodel

When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Altar of the Brood

Whenever another permanent you control enters, each opponent mills a card.

Exquisite Blood

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

Fleshbag Marauder

When this creature enters, each player sacrifices a creature of their choice.

Merciless Executioner

Undercity Informer

{1}, Sacrifice a creature: Target player reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Dread Summons

Each player mills X cards. For each creature card put into a graveyard this way, you create a tapped 2/2 black Zombie creature token. (To mill a card, a player puts the top card of their library into their graveyard.)

Swamp

Dreadhound

When this creature enters, mill three cards. (Put the top three cards of your library into your graveyard.)
Whenever a creature dies or a creature card is put into a graveyard from a library, each opponent loses 1 life.

Sanguine Bond

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

Ghoulcaller's Bell

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Balustrade Spy

Flying
When this creature enters, target player reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on this enchantment. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if this enchantment has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.