Dislodged in a final offensive by a Kurdish-led ground force and coalition air strikes, thousands of wives and children of IS fighters have flooded in from a string of Syrian villages south of the camp in recent months.
Among the hordes of Syrians and Iraqis, some 9,000 foreigners are held in a fenced section of the encampment, under the watch of Kurdish forces.
When they want to go to the camp's market or receive aid rations, these high-risk prisoners are escorted by armed guards.
But tensions are rife among the foreigners themselves.
"We don't have the same mentality -- they (the extremists) want to impose their vision of Islam," said Vanessa, who came to Syria from her native Guyana as a convert in 2013 with her husband and children.
"They say that we are infidels," the gangly 36-year-old said, singling out the camp's Tunisians as especially "extreme".
The semi-autonomous Kurdish administration that rules much of northeastern Syria is urging countries of origin to take back their citizens.
The women and children need to be "re-educated and reintegrated by their home countries," said Kurdish official Abdel Karm Omar.
Otherwise, he warned, they will become "the terrorists of the future".
- 'These people scare me' -
Under IS's so-called caliphate -- declared in 2014 over large swaths of Syria and neighbouring Iraq -- minors were systematically indoctrinated and even exposed to public executions.
In a gesture of continued loyalty to IS, some children at the camp -- a few grinning, others staring coldly -- pointed their index finger to the sky in front of AFP reporters.
One woman threatened to hit a cameraman, but others -- anxious to return home and declaring they regret joining IS -- were keen to talk.
Some of the Tunisians and Russians interned at Al-Hol have adopted "very extreme beliefs", confided a Belgian woman who came to Syria in 2013.
"These people scare me", she said.
Even just "talking to the guards, or requesting to go to the market, can make us infidels" in their eyes, she added.
Once someone is labelled a non-believer, these women decree it lawful to strip the person of their belongings, the Belgian said.
"They can burn our tents and do whatever they want to us."
But tensions are not limited to the foreigners' section.
A few days ago, a confrontation escalated in the main area, populated by Iraqis and Syrians. Kurdish police were forced to intervene.
Some of the residents "threw stones" at their fellow residents, a policeman told AFP, without giving his name.
Nabil al-Hassan, who heads the camp's communications, insisted the "security situation is under control".
But, he admitted, major logistical challenges give rise to "problems", including tensions over access to tents and aid.
- 'It's not mine' -
Heavily pregnant Lamia, 21, told AFP she is steadfast in her loyalty to the IS cause.
"We remain with the (Islamic) State," said the former resident of Manbij, a northern Syrian town that was occupied by the jihadists until the Kurdish-led Syrian Democratic Forces prevailed.
Lamia wants to go back to her hometown and has been at the camp for a month; her first husband was killed in combat, the second is in prison.
Back at the entrance to the foreigners' area, several women including Algerians and Ukrainians gathered at the gate, insisting it was their turn to go to market.
Blonde children and those from central Asia mingled in the dust.
The women returned from the market hauling trolleys full of eggs, potatoes, nappies, and gas cylinders.
Everything is meticulously searched by the guards, who are instructed to confiscate, log and store unusually valuable items and mobile phones.
These "security measures" are needed to stop residents stealing from each other -- and from smuggling goods or cultivating contacts in the outside world -- Hassan said.
Delving through a black handbag, the guards retrieved a phone and small piece of paper with a contact number scrawled on it.
"It's not mine, it belongs to my friend," the Tunisian owner insisted.
A little later, in another bag, the guards dug out a ring and a hefty gold chain, carefully hidden in a tiny plastic bag.
The dismayed owner gripped the sentinel's hands in an attempt to prise back the items, to no avail.
"She's not coming back inside. Take her to the cell," the guard said.
The woman clung to the wire fence and wailed.