Malenia first appeared in the video game Elden Ring, serving as an optional boss fight available later in the game. Within the game's lore, she is the demigod child of Queen Marika and her second husband, Radagon. Alongside her twin brother Miquella, Malenia was born as an Empyrean, a powerful being chosen as a candidate to create a new age and rule it as a god. In Malenia's case, she was cursed with Scarlet Rot, a devastating disease caused by a godlike being, and one that begins to putrefy her body. In an attempt to save Malenia from being consumed, Miquella utilized Unalloyed Gold, a material capable of warding off the influence of Outer Gods, to break the rot god's influence on her. Malenia learned her combat style from a nomadic character called the Blind Swordsman. Mastering his technique gave her "wings of unparalleled strength", while also helping her resist the rot.
During a civil war known as the Shattering, Malenia led her knights on an undefeated campaign across the land, winning many victories, including against at least one fellow demigod relative. Her campaign eventually brought her into conflict with her half-brother Starscourge Radahn, with her encountering heavy resistance from his army before the two demigods met each other and dueled to a stalemate. At the end of their battle, Malenia unleashed the Scarlet Rot and lost her special Unalloyed Gold needle. With both sides unable to claim true victory, she lost control of the disease and Malenia herself was dragged unconscious by one of her few remaining knights to the Haligtree, a holy tree created by Miquella. After Miquella is kidnapped, she inadvertently causes the tree to rot from the inside during her slumber. She awakens when the player encounters her at the base of the Haligtree's interior, engaging them in battle. If the player manages to deal enough damage to her, she is overcome by the rot once more, becoming Malenia, Goddess of Rot.