16 cards where the name includes “altar” and the card types include “artifact”

Altar Golem (Eventide #166)
Altar of Bhaal // Bone Offering (Commander Legends: Battle for Baldur's Gate #109)
Altar of Dementia (Modern Horizons #218)
Altar of Shadows (Mirrodin #143)
Altar of the Brood (Khans of Tarkir #216)
Altar of the Goyf (Modern Horizons 2 #220)
Altar of the Lost (Dark Ascension #144)
Altar of the Pantheon (Theros Beyond Death #231)
Altar of the Wretched // Wretched Bonemass (The Lost Caverns of Ixalan Commander #10)
Altar of the Wretched // Wretched Bonemass (The Lost Caverns of Ixalan Commander #10)
Ashnod's Altar (Commander Masters #368)
Baku Altar (Betrayers of Kamigawa #152)
Bloodsoaked Altar (Core Set 2020 #90)
Carnage Altar (Commander 2013 #238)
Netherborn Altar (Commander 2020 #45)
Phyrexian Altar (Double Masters 2022 #311)
Transmogrant Altar (The Brothers' War #124)

Though this query has ended, its relics still slumber in New Argive.