The black-snake, prophesy said, would only be overcome by the Seventh Generation, which would rise up and, as Charger explained, “bring balance to the Earth. Not just to its people. To the Earth.” Many of the youths that I spoke with took this to mean the Seventh Generation had a sort of messianic role to help restore order, on behalf of all beings, to a world thrown out of balance by modernity and greed.

“The Seventh Generation is almost cliché in Indian communities,” Goldtooth, the I.E.N. organizer told me. Anyone born between 1980 and the 2000s, he said, “hears about it constantly. The hope that our generation will see a significant shift toward community renewal and nation building and the reminder that our communities expect big things of us.” The Seventh Generation tracks roughly with millennials of all races, but they share their own unique history. The generation between Goldtooth, 34, and Charger, now 20, is the first to have grown up free to be Indian. They are familiar with their ancestors’ scars but also fluent in mainstream American culture.

At Standing Rock, the elders, once resistant to their movement, now insisted that the youths accept the responsibility that the prophecy had foretold. In early September, the Seven Council Fires and Chief Arvol Looking Horse, who, for the Lakota Sioux, is something like their head of religion, gave the youths a gift: a chanupa, the ceremonial pipe that is the most sacred element of the Plains religion, a symbol of the knitting together of the human community and nature, ancestors with the living. In a ceremony under the blazing sun, the council deputized the youths as akicita, a Lakota term that means something like “warriors for the people” or “police.” It is difficult to overstate the importance of this gesture. The youths, Looking Horse explained to me, “weren’t really ready for it, but we told them that they’re going to accept it and learn the traditions. We said they had to be of pure mind. They said, ‘We’ll try.’ ”

After the ceremony, the youths, who had begun to call themselves the International Indigenous Youth Council, or I.I.Y.C., to symbolize their desire to unite all nations behind a traditional way of life, moved together into a tepee by the Cannonball River. “A lot of our first month or two living together,” Wise said, “was just having someone break down crying.” In her short time at the camp, Wise had become a sort of surrogate mother to the other young people — her nickname even became Ina, or “mother” — and she found herself in charge of a group of about 25 who were barely holding it together, despite the leadership they had assumed. The I.I.Y.C. was the first experience of family for many members. “A lot of them never had the opportunity to be kids, because they were always trying to take care of themselves or take care of their parents.” This process, one of the youth leaders told me, was “terribly beautiful,” an unburdening of the “historical trauma” that had defined their lives. “No one realizes what the repercussions of colonization have been, the repercussions of forced removal,” Wise said. It was hard, she stressed, to explain to people that these were things that had happened recently, to her generation’s parents and grandparents.

“I don’t blame my mom,” Charger told me. “Her mother was murdered.” She shrugged. “The abuse lives in our blood.”

Charger was referring to Native American history, not just what happened on the frontier but also in more recent decades. After federal campaigns reduced the Oceti Sakowin in the late 1800s, there were nearly 100 years of calculated assault as the state tried to force Native Americans to assimilate. The unified nation of Oceti Sakowin was broken into widely separated reservations, and after Congress privatized reservation land, many starving Lakota families had to sell off their property to white farmers, further cutting the size of reservations. The U.S. Government banned the Sundance, the Plains religions’ most sacred ceremony, with its days of fasting and ritual bloodletting; Native Americans could no longer openly practice their religions. But perhaps most devastating to their psychological health were the boarding schools, in which generations of Indians were sent to schools to be taught white culture. This system reached its nadir in the forced assimilation campaigns of the 1940s and 1950s, when the grandparents of many of the I.I.Y.C. youths were taught English literally under the lash.

At Standing Rock, the youths felt they were developing the means to overcome that trauma. The key, as Charger explained it, was to let their history go, which they took as an almost holy responsibility: Forgive, and then take action to spare those who are coming in the future. “We don’t want our children to inherit this depression,” she said. The remarkable thing about this philosophy was that it was deeply practical: not just forgiving “the white man” but also the parent who beat you. For many, this provided a means to re-establish difficult relationships with parents or siblings. But it also helped bind them together into their own sort of family.