"Phyrexian Altar," from the Magic: The Gathering Invasion set, is an Unknown rarity card numbered #306. Valued at $53.08, it serves as a strategic resource for players looking to enhance their deck's performance through the sacrifice of creatures for mana. Its unique ability to convert creatures into mana has made it a sought-after card in various formats, contributing to its steady market value. Collectors appreciate its role in both gameplay and as a collectible item.