Card

Altar of Dementia

Mana cost {2}

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

Part of 2,283 known combos, 4 of them two-card. 2 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Jumbo Cactuar, Kroxa and Kunoros, Young Necromancer, Body of Research
B2 Core — Not in the same deck as its two-card combo partners: Jumbo Cactuar, Kroxa and Kunoros, Young Necromancer, Body of Research
B3 Upgraded — Not in the same deck as its early two-card combo partners: Jumbo Cactuar, Kroxa and Kunoros, Young Necromancer, Body of Research
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Jumbo Cactuar, Kroxa and Kunoros, Young Necromancer, Body of Research (early with Jumbo Cactuar, Kroxa and Kunoros, Young Necromancer, Body of Research)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

2,283 known combos, 4 of them two-card.

Mikaeus, the Unhallowed + Altar of Dementia
Produces: Infinite creature ETB, Infinite creature LTB, Infinite creature sacrifice triggers
View on Commander Spellbook
Luminous Broodmoth + Altar of Dementia
Produces: Infinite creature LTB, Infinite creature ETB, Infinite creature sacrifice triggers
View on Commander Spellbook
Gravecrawler + Pitiless Plunderer + Altar of Dementia
Produces: Infinite death triggers, Infinite creature ETB, Infinite creature LTB
View on Commander Spellbook

2019-06-14 · 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.
2019-06-14 · 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.

Rulings: Scryfall · Wizards of the Coast