Yazidi faith has roots in Islam but shunned by some Muslims

The Yazidi faith is a mix of ancient religions.

Its reputed founder was an 11th-century Umayyad sheik whose lineage connected him to the first great Islamic political dynasty. His tomb in the Iraqi city of Lalish is a site of Yazidi pilgrimage, mirroring the Sufi practices of millions of Muslims elsewhere.

Despite its connections to Islam, the faith remains distinctly apart. It was one of the non-Abrahamic creeds left in the Middle East, drawing on various pre-Islamic and Persian traditions. Yazidis believe in a form of reincarnation and adhere to a strict caste system.

Yazidism borrows from Zoroastrianism, which held sway in what's now Iran and its environs before the advent of Islam, and even the mysteries of Mithraism, a quasi-monotheistic religion that was popular for centuries in the Roman Empire, particularly among soldiers.

Yazidis believe in one God who is represented by seven angels. According to Yazidi lore, one of the angels, Malak Tawous, was sent to Earth after refusing to bow to Adam, explains the Economist.

Represented in peacock form, he is considered neither wholly good nor evil by Yazidis, but Muslim outsiders know him as "shaytan," or Satan.

The Yazidis, globally, number about 700,000 people, but the vast majority of the community -- about half a million to 600,000 -- live concentrated in Iraq's north.

The Islamic State extremist group has justified its current offensive against the Yazidis on the basis of the long-standing slur that they are "devil-worshipers."

The Yazidis' fragile existence in northern Iraq grew more delicate after the 2003 U.S.-led invasion of the country and the ousting of Saddam Hussein's nominally secular dictatorial regime.

In 2007, coordinated bomb blasts in a Yazidi village in northwestern Iraq killed about 800 people -- it was at the time the worst single terror attack since the American invasion.