Altar of Dementia — ruling 1

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.

Altar of Dementia — ruling 2

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.

Altar of Dementia : règles, fonctionnement et interactions (MTG)

Altar of Dementia is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

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

Complete guide

Altar of Dementia is a powerful artifact that turns your creatures into a source of deck destruction. Whether you are aiming to win by emptying an opponent's library or filling your own graveyard for recursion, this card is a versatile engine. Its ability to sacrifice creatures at instant speed makes it a dangerous tool in any strategy that values the death of its own units.

What It Does

Altar of Dementia features a single activated ability that costs no mana to activate. By sacrificing a creature, you force a target player to mill cards equal to that creature's power. Because the cost is sacrificing a creature, this ability can be used to respond to removal spells or to get value out of creatures that were going to die anyway.

How It Resolves Step by Step

First, you announce the activation and choose a target player. Second, you pay the cost by sacrificing a creature; this is when the game checks the creature's power as it last existed on the battlefield. Finally, once the ability resolves, the target player moves the top cards of their library to their graveyard. If the creature had its power boosted by equipment or spells before being sacrificed, the mill amount will reflect that higher value.

Common Mistakes

A common misconception is that a player loses immediately if they have to mill more cards than remain in their library. According to official rulings, if a player has fewer cards than the creature's power, they simply mill everything they have left. They do not lose the game until the next time they are required to actually draw a card from an empty library.

When to Play It

You should play Altar of Dementia when you have a deck that can generate many creatures or large creatures. It is especially effective in 'Aristocrat' style decks where you want a free way to trigger death abilities, or in 'Dredge' and 'Reanimator' decks where targeting yourself can help set up your future turns.

Interaction examples

Fast Mana Setup

Sol Ring

With a Sol Ring on the battlefield, you can tap it to add two colorless mana, allowing you to cast Altar of Dementia as early as turn one. This sets up your sacrifice outlet before you even play your first creature.

Fixing for the Altar

Arcane Signet

In a multi-color deck, using Arcane Signet ensures you have the mana variety needed to cast the creatures you intend to sacrifice to the Altar of Dementia later in the game.

Basic Mill Action

If you control a creature with 5 power and sacrifice it to the Altar, the target player mills exactly 5 cards. The game looks at the power the creature had just before it left the battlefield to determine this number.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Altar of Dementia

Original English text — Wizards of the Coast / Scryfall

#1June 14, 2019· Wizards of the Coast
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.
No other card is named in this ruling.
#2June 14, 2019· Wizards of the Coast
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.
No other card is named in this ruling.