Acknowledged as the founder of Adevviye Cult, Adî b. Müsâfir was born in the Beytifâr village of Ba’lebek city in Syria. Leaving there after a certain age, he secluded himself in Hakkâri mountains and preserved the mission of showing the true path until his death in the hermitage he built there. Here, he established the Adevviye Cult named after him and based on piety and devotion. Although he was known for his piety and devotion and following the way of the Qur’an and the Sunnah in accordance with Sunni Islam belief, his disciples have exceeded the love for him and after some time the Adevviye Cult has unfortunately transformed into a void sect called as Yazidi. The Adevviye Cult, its founder Adî b. Müsâfir, and the transformation of this cult into Yazidi will be studied in this essay.