Its name means "multitude," and it may be the biggest and most dangerous gang in the world, a thuggish army terrorizing Kenya with extortion rackets and gruesome punishments.
Much about the organization called Mungiki is cloaked in myth and speculation, not least the estimate of sworn members -- some say 100,000, others say millions. Those claiming to be defectors, however, say the gang relies on strict discipline and tolerates no dissent.
"If a member disobeys, they would cut that member's head off and put the head in public view at the place where they had a problem with the member," an alleged former member said in a statement to prosecutors at the International Criminal Court.
Six Kenyans are facing charges at the ICC related to the ethnic violence that brought Kenya to the brink of civil war in late 2007-early 2008. The proceedings in The Hague in the Netherlands have cast a spotlight on the workings of the secretive Mungiki and its alleged role in what the court charges was government-sponsored mayhem in the wake of a disputed presidential election that left more than 1,000 people dead.
Often referred to in the Kenyan press as "an outlawed sect," Mungiki has roots as a religious movement of the Kikuyu, Kenya's most populous ethnic group.
Some call it a descendant of the 1950s-era Mau Mau movement, in which Kikuyu guerrillas battled the British colonial establishment under the banner of "Land and Freedom."
Central to the ICC case is the nature of the gang's links to the Kenyan government, despite a bloody, controversial battle to crush the group.
Prosecutors contend that chilling attacks by Mungiki thugs in the Rift Valley towns of Naivasha and Nakuru against members of the Luo ethnic group were orchestrated by one of Kenya's most famous figures, Uhuru Kenyatta, son of the country's first president and currently its finance minister and deputy prime minister.
"Mr. Kenyatta had close and powerful ties with Mungiki, ties that went back many years," prosecutor Adesola Adeboyejo told a pretrial chamber at The Hague in September.
Prosecutors, who have not publicly revealed many witnesses' names on security grounds, pointed to statements from alleged Mungiki insiders who claimed that Kenyatta swore an oath of membership in the gang.
Starting in December 2007, prosecutors contend, Kenyatta met Mungiki leaders multiple times, sometimes at State House, Kenya's White House, to plan the attacks in the Rift Valley towns. At one meeting, according to a witness, Kenyatta distributed 3.3 million Kenyan shillings -- about $36,000 -- to people he charged with carrying out the attacks.
Another witness, claiming to be a former gang member, alleges that he received a text message on his cellphone ordering him to board a bus that took him to State House, where he and dozens of other members were assured of government support and driven to Naivasha to attack civilians.
Despite long-standing public animosity between Kenyan police and Mungiki, prosecutors allege, police allowed gang members to roam from house to house, targeting mostly Luo supporters of presidential challenger Raila Odinga, a Kikuyu, who claimed he had been cheated out of the presidency.
Prosecutors contend that Kenyatta orchestrated the attacks with Francis Muthaura, the head of the civil service, who allegedly ordered police not to interfere.
Kenyatta appeared as a witness before the pretrial chamber in September and denied that he had ever belonged to the gang. The gang had, in fact, burned him in effigy in August 2000, apparently blaming him for a government crackdown.
The claim that he distributed millions of shillings at State House was "completely ludicrous," Kenyatta said. Though Mungiki backed his failed bid for president in 2002, he said, he did not solicit that support, and had repeatedly denounced the gang's activities.
The ICC's chief prosecutor, Luis Moreno-Ocampo, cross-examined Kenyatta but appeared to make little headway. At one point, Moreno-Ocampo told Kenyatta that he was "the only link" between the Mungiki violence and Kenya's ruling coalition.
"Our theory, our evidence shows that you were calling the Mungiki, that you were organizing them, you were financing them," Moreno-Ocampo said. "But maybe this is a chance for you to explain to us now it is a different person who did that."
Kenyatta again denied any link with the gang.
Embodying the gang's enduring enigma is Maina Njenga, who was long described in the Kenyan press as its boss. In 2009, Njenga was incarcerated on murder charges but released after he threatened to reveal an affidavit detailing links between government and the gang.
Since then, according to accounts in the Kenyan press, Njenga claims to have been born again as a Christian "ambassador of peace," and announced that he would turn his Mungiki followers -- who he claimed numbered in the millions -- to positive political action.
Paul Muite, a Nairobi attorney who represented Njenga in the murder case, said his Christian conversion appeared to be a function of survival amid the violent crackdown. "He wants to save his life," Muite said.
Muite said the gang is hugely popular among desperate, disaffected Kikuyu youths. "They have no stake in life. They have no hope, no future," Muite said. "For young people, [Njenga] is a messiah."
A much-debated question is how large and how dangerous Mungiki actually is. Some say it is a band of directionless Kikuyu youths who use the gang's mystique, and its echo of secret Mau Mau rituals, to terrify victims who can't discern genuine members.
"Mungiki has become a brand name. Anybody who wants to intimidate, who wants to extort -- ordinary criminals -- say they're Mungiki," Muite said.
On a recent day in the Nairobi slum of Mathare, Stephen Mwangi, 30, described himself as a former foot soldier for the gang. He said he grew up in the slum, then a Mungiki stronghold with about 2,000 other members.
"People you grow up with join, and you also join," Mwangi said. "Once you were a member of the gang, you were feared."
Like other members, Mwangi said, he charged slum dwellers for illegal power line connections and for protection, patrolling the streets with a club or machete. He also extorted money from matatu, or minibus, drivers.
Now, Mwangi said, the gang is largely gone from Mathare, and he sells firewood elsewhere in Nairobi to support his family. He said the government crackdown, in which 10 of his friends were killed by police, drove him from the gang.
"Whoever was found collecting money from matatus, he was taken to be a member of the gang," Mwangi said.
"They would just disappear."