https://eldenring.wiki.fextralife.com/Malenia+Blade+of+Miquella

Malenia, Blade of Miquella is a Boss in Elden Ring. Born as a twin to Miquella, Malenia is known as the most powerful of the Empyreans. Wielding a prosthetic arm and leg, Malenia is located in the Consecrated Snowfield. This boss is optional, as players do not need to defeat it in order to advance in Elden Ring. Malenia is also the feature of the game's Collector's Edition, which features a statue of her and a replica of her helmet.