WASHINGTON — It’s tragic that the world pays attention to largely forgotten communities only in their moments of greatest peril. This week, we’ve watched as tens of thousands of Yazidis – a mostly Kurdish-speaking people who practice a unique, syncretic faith – fled the advance through northern Iraq of the Islamic State’s Sunni jihadists, who have set about abducting and killing hundreds of members of this religious minority.

As The Washington Post reports, as many as 40,000 remain stranded on “the craggy peaks of Mount Sinjar,” dying of hunger and thirst and devoid of much support from a faltering Iraqi government.

Ever since seizing Mosul, Iraq’s main urban center in the north, the forces of the Islamic State have embarked on a gruesome mission to transform their domain into an idealized Caliphate – on the way, they’ve forced the conversion of religious minorities, destroyed the shrines of rival sects and butchered those they consider apostates.

This week, a distraught Yazidi member of parliament in Baghdad made an impassioned appeal on behalf of her people: “An entire religion is being exterminated from the face of the Earth,” she said.

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 city of Sinjar was their heartland. Now, it’s in the possession of extremists who seem bent on ethnic cleansing.

The Yazidi faith is a fascinating 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; now, there are reports of the town being turned into a refugee camp for the displaced.

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.

Not unlike the rituals of India’s Parsis – latter-day Zoroastrians – Yazidis light candles in religious ceremonies as a sign of the triumph of light over darkness.

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 Islamic State has justified its slaughter of Yazidis on the basis of the long-standing slur that they are “devil-worshippers.”

Bobby Ghosh, former Time magazine Baghdad bureau chief, writes that his Sunni and Shiite colleagues referred to Yazidis as devil-worshippers “as a joke, even a term of endearment.” But the Islamic State “is taking the false claim of satanism far too seriously.”

Well before the current outrages – which have targeted other religious minorities in Iraq as well – the sect suffered a long history of persecution, caught amid the overlapping ambitions of empires and later the emergence of fractious Arab states.

The Yazidi member in the Iraqi parliament referenced “72 massacres” in her people’s history, ranging from the rampages of conquering Mongols to the zealous purges of the Ottomans, who at various moments targeted the Yazidis, including during the early 20th-century massacres of Armenians that many now consider a genocide.

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.

After Baghdad’s deeply polarized sectarian politics took hold and militants gained sway, much of northern Iraq’s ancient Christian population has steadily fled to diasporic communities in Europe. The Yazidis largely remained in their historical homeland, by their mountains and shrines.

That life, though, also may now be a thing of the past.

Tharoor writes about foreign affairs for The Washington Post. He previously was a senior editor at TIME, based first in Hong Kong and later in New York.