Cyäegha is an obscure Great Old One, and is characterized by its supreme nihilism and utter contempt for all things. The being appears as a great, black-bodied, green eye surrounded by a mass of tentacles. Cyäegha is served by toad-like monsters known as the Nagäae (possibly a derivative of "Nagae").
Cyäegha has existed since the dawn of time, and sleeps within a vast cavern underneath the (probably fictitious) mountain of Dunkelhügel, the "Dark Hill", in Germany. The inhabitants of the nearby farming village of Freihausgarten are descended from a cult who once worshipped Cyäegha. Cyäegha's worshipers draw upon the deity for vitality, but also greatly fear awakening the god for its wrath is said to be terrible.
Cyäegha's cult became active within the town of Freihausgarten in the 17th century, and remained so well into the 19th century. In 1860, the cult was soon disbanded by a young priest, who died while battling Cyäegha. However, once a month, on the night of the full moon, the descendants of the former cultists are drawn towards Dunkelhügel by the hypnotic telepathic pull of Cyäegha. Once there, they are compelled to climb the Dark Hill, and perform an ancient ritual which both appeases and binds Cyäegha. However, despite performing this ritual every month without fail, the villagers are not even aware that they had practice the rite, and continue to fear the mountain and ordinarily avoid it.
The five Vaeyen
Cyäegha is both protected and imprisoned by five lesser demons known as the Vaeyen. They are "The Green Moon", "The White Fire Which Is Darker Than The Night", "The Winged Woman", "The White Dark Which Is More Red Than The Fire", and "The Black Light". The spirits of these guardians are contained within five vulturine statues which Cyäegha's worshipers use to keep their god in check.
Cyäegha is an earth elemental, and is said to be a cousin of Nyogtha, another earth elemental. Cyäegha is also believed to be related to the Great Old One Othuyeg, because each appear alike and have similar habits. Like all the other Derlethian earth elementals, Cyäegha is adversely affected by the Ankh or Crux Ansata, the Vach-Viraj ritual, and the Tikkoun Elixir. References to Cyäegha are found in the Necronomicon, the Unaussprechlichen Kulten, the R'lyeh Text, the Cthäat Aquadingen, and a few more obscure grimoires.