Commander creatures you own have "Whenever an artifact or creature you control is put into a graveyard from the battlefield, each opponent loses 1 life."

Whenever this creature or another creature dies, target player loses 1 life and you gain 1 life.

Horrors you control have menace. Whenever a Horror you control deals combat damage to a player, that player mills that many cards. At the beginning of your end step, choose target artifact or creature card in an opponent's graveyard that was put there from their library this turn. Put it onto the battlefield under your control.

At the beginning of each player's upkeep, that player mills X cards, where X is the number of cards in their hand.

{1}{U}{B}: Whenever a card is put into an opponent's graveyard from anywhere this turn, that player loses 1 life. {2}{U}{B}: Target player mills two cards.

Enchant player At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.

Landfall — Whenever a land you control enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)

Each opponent reveals cards from the top of their library until they reveal X land cards, then puts all cards revealed this way into their graveyard. X can't be 0.

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

Whenever you draw a card, each opponent mills two cards.

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Descend 8 — The Ancient One can't attack or block unless there are eight or more permanent cards in your graveyard. {2}{U}{B}: Draw a card, then discard a card. When you discard a card this way, target player mills cards equal to its mana value.

The Mindskinner can't be blocked. If a source you control would deal damage to an opponent, prevent that damage and each opponent mills that many cards.