They are Kurds who hold a pre-Islamic religion - mixing Zoroastrian with Jude-Christian beliefs. They also worship Lucifer but see him in a positive light.
https://en.wikipedia.org/wiki/Yazidis
The Yazidi people speak Kurmanji Kurdish with a religion rooted in Iranian religions blended with elements of pre-Islamic Mesopotamian religious traditions.
The Theosophical Society, in its electronic version of the Encyclopedic Theosophical Glossary states: Yezidis (Arabic) [possibly from Persian yazdan god; or the 2nd Umayyad Caliph, Yazid (r. 680–683); or Persian city Yezd] A sect dwelling principally in Iraq, Armenia, and the Caucasus, who call themselves Dasni. Their religious beliefs take on the characteristics of their surrounding peoples, inasmuch as, openly or publicly, they regard Mohammed as a prophet, and Jesus Christ as an angel in human form. Points of resemblance are found with ancient Zoroastrian and Assyrian religion. The principal feature of their worship, however, is Satan under the name of Muluk-Taus. However, it is not the Christian Satan, nor the devil in any form; their Muluk-Taus is the hundred- or thousand-eyed cosmic wisdom, pictured as a bird (the peacock).
Does the “bird” (peacock) refer to the Persian royalty (The Peacock Throne)?