Yidhra, called the Dream Witch, is an Outer God said to have existed since before life arose on Earth. She devours other lifeforms and assimilates their evolutionary traits and memories, gaining the power to take on their shapes or reproduce their body parts. Having absorbed countless lives and reshaping herself without end, she has no fixed true form, and appears to her worshippers as the illusion of a young, beautiful woman.
Worshipped as an earth-mother, she superficially resembles Shub-Niggurath, though the sources treat the two as distinctly separate beings. Originally devised by Walter C. DeBill Jr. for his own "Mlandoth" mythos, she entered the wider Cthulhu Mythos by way of the story "Where Yidhra Walks" (1976) and Chaosium's tabletop RPG Call of Cthulhu. She manifests around the world through avatars such as Yolanda and Madam Yi, and is served by cults like the Children of Yidhra and the all-female Mothers of Woe.
Yidhra's horror lies less in any monstrous shape than in how she survives. She becomes everything she consumes and so lives forever, and she pours dreams and visions straight into her followers' minds, letting them see only what she wishes. Her beauty and her benevolent maternal face are her deepest disguise; the dread comes from never knowing what one is truly facing.