"My dreams have brought more visions from our master: an altar, exquisite and perfect. We must build it at once."
—Writings of Artonac, priest of Gix

Altar of Dementia

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

"It is not that you will go mad. It is that you will beg for madness."
—Volrath

The Brothers' War Retro Artifacts

Modern Horizons

Sacrifice a creature: Target player puts a number of cards equal to the sacrificed creature's power from the top of their library into their graveyard.

Conspiracy

Sacrifice a creature: Target player puts a number of cards equal to the sacrificed creature's power from the top of his or her library into his or her graveyard.

If the target player's library contains fewer cards than the sacrificed creature's power, all of those cards are put into that player's graveyard. That player won't lose the game until they try to draw from the empty library.

The number of cards the target player puts into their graveyard is equal to the power of the sacrificed creature as it last existed on the battlefield.