Selene is a Changeling, a rare forest spirit found in Valenwood. She is also a powerful sorceress and the High Priestess of Shagrath, the Godess of Spiders. She possesses the ability to shift form between a giant spider and a female humanoid. Her domain is known as Selene's Web.
Originally, Selene was a reclusive forest spirit who had done nothing to harm mortals. In 2E 582, Warlock Carindon of the Mages Guild launched an expedition into the forests of Selene's Web to research Selene, who was the first Changeling the guild had heard of in thousands of years. Unbeknownst to the other expedition members, Carindon planned to kill Selene and steal her soul for dissection, despite a deal she had made with the guild to be left in peace. Carindon also hired a band of Undaunted adventurers for protection. At the time, Selene was worshipped by a tribe of Bosmer and several Khajiit, to whom she granted "spirit life" upon death. Along with her army of woodland creatures, her followers attempted to keep the intruders at bay. Only Carindon and the four adventurers succeeded in reaching her inner sanctum, where Selene was slain and her soul captured. Carindon planned to publish a codex from the knowledge he would obtain from her spirit. He planned to use her aura for various potions, and study her ability to spin "arcane threads" in order to utilize it in a multitude of spell types.
Her head later found its way onto one of the adventurer's walls as a hunting trophy, to increase the adventurer's prestige among the Undaunted. Her image was also used by the Undaunted in their armor.
Some time after this, Selene was freed and constructed a fortress in Selene's Web. She began consorting with undead, and infused her lifeforce into a great jewel, the Heart of Selene. During the Imperial Simulacrum, she began to spread her dark influence throughout Valenwood, draining corpses of all fluid and raising them as living dead with no memories of their former existence. The city of Elden Root sent out scouts to investigate, and Selene sent back an emissary with their decapitated heads. She gave the Bosmer an ultimatum: "surrender Valenwood or die". With no standing army, the peaceful Bosmer had no means to defeat her army of spiders and undead. Queen Ulandra of Elden Root struck a deal with the Eternal Champion, offering the sacred location of Elden Grove in exchange for the Heart of Selene. The Champion then infiltrated Selene's Web and claimed the jewel. With it, Ulandra was able to blackmail Selene into calling off her attacks with her life now hanging in the balance.