Unjustly regarded as 'devil worshippers' on account of their unusual beliefs, the Yazidi have for centuries been one of the most persecuted minorities of the Middle East.
Islamic extremists regard them as infidels, worthy only of being killed.
They are an ethnic Kurdish people who tend to have fairer complexions than many in the Middle East.
They regard wearing blue as sacrilege, they never eat cabbage or lettuce and their men often have long beards and wear their hair in plaits – which make them resemble the cartoon characters of ancient Gaul, Asterix and Obelix.
They adhere to a 4,000-year-old faith passed down and adapted through the generations by word of mouth and composed of elements of several religions.
Their reverence for fire and light derives from the ancient faith called Zoroastrianism, the religion of Persia long before Islam arrived.
They combine such Christian practices as baptism with Jewish or Islamic circumcision. Like Buddhists they believe in perpetual reincarnation.
But it is the central tenet of their religion that has led others to brand them devil worshippers.
They believe in one God who illuminated seven angels with his light.
The greatest of the seven is the Peacock Angel, known as Malak Taus, who is dressed in blue (which is why the Yazidi refuse to wear the colour).
His other name is Shaytan, Arabic for the devil or Satan.
The Yazidi believe that God left the Earth in the care of the seven angels and told them to obey Adam.
The Peacock Angel refused, stating that Adam was created from the soil, and God’s light could never be at the mercy of the soil.
He was cast out for his disobedience, but was quickly reconciled with God who respected his argument – which proved he was, in fact, the most loyal angel of all.
This is why the idea that he was akin to Lucifer is so misleading.
Tragically, the Yazidi are also victims of another misunderstanding, over their name.
Sunni extremists believe it derives from a deeply unpopular seventh century caliph – or leader – Yazid ibn Muawiya.
In fact, it comes from the Persian word for angel or deity, 'Ized'. Their name simply means ‘worshippers of God’.
Yet no such theological distinction interests Islamic State fighters in a Middle East where minor divergences between Sunni and Shia Muslims are a matter of life and death, and the region's 12million Christians are diminishing by the day.
In such a murderous atmosphere, ‘Satan worshippers’ are inevitably the targets of genocidal fanatics.
Even to ordinary Iraqis, they are seen as bogeymen to frighten children with.
The Yazidi once lived in a wide area across Iraq, Syria, Turkey, Georgia and Armenia.
But successive waves of persecution - they claim to have survived 72 genocides - by the Ottoman Turkish rulers of what is now Iraq, by Saddam Hussein and now by Islamic militants, have reduced the number of Yazidi from millions to an estimated 700,000.
In recent years, some 70,000 have fled to Europe, where 40,000 live in western Germany.
This is not surprising. Since the Yazidi welcomed the US invasion of Iraq after 2003 and admire Israel, they attracted the malevolence of Al Qaeda and other jihadists before the Islamic State came on the scene; in 2007 massive truck bombs killed 500.
What makes the Yazidi still more vulnerable is the insular nature of their community. No one can convert to their religion, you have to be born into it. They also practice endogamy – that is, they only marry members of the same faith.
They believe that when someone dies, their soul passes into a new member of the community and that purification of the soul is only possible through continual rebirth.
The worst possible fate, therefore, is to be expelled from the community because the soul can never then be purified or saved.
Equally, anyone who voluntarily leaves the religion risks death. In 2007, it was reported that Du’a Khalil Aswad, a Yazidi woman, was stoned to death for converting to Islam and marrying a Muslim man.
Feared, villified and slaughtered for centuries, it is in many ways remarkable such a strong community of Yazidis still exists at all. But now, with the Islamic State’s determination to wipe them out, they perhaps face their greatest test of all.