The court heard accounts of racist rampages fuelled by drugs and drink, violent assaults in a garage draped with Swastika flags and portraits of Hitler and the humiliation and beating of a member suspected of disloyalty.
One of the accused did not turn up for the trial.
Among the others is 57-year-old Serge Ayoub, alias Batskin, who was the leader of a far-right skinhead gang, the Troisième Voie (Third Way) and Jeunesses Nationalistes Révolutionnaires (Revolutionary Nationalist Youth - JNR), before it was banned because of the killing of antifascist activist Clément Méric in 2013.
"I've got nothing to do with what happened," he told the court. "I've already said it again and again [...] I don't understand what I'm doing here."
Nazi flags, Hitler portraits, beatings with motorbike chain
Another defendant, Kévin Pate, testified that Ayoub had told them to "sort that out [...] which means hit someone" when questioned about the assault of members of a rival group that had called the veteran far-right leader a "dirty Jew" in 2012.
The victims, one of whom was kicked, hit with a motorcycle chain and stabbed, were beaten up in a garage decorated with Nazi flags and portraits of Adolf Hitler that belonged to Jérémy Mourain, at the time the Picardy regional leader of the JNR and later leader of the WWK.
"We're racist, so that's why we put up flags like that," Pate told the court.
The seven accused of involvement in that assault have confessed to their role but Mourain has refused to implicate Ayoub.
Several violent incidents under the influence of alcohol and cocaine feature in the case, among them a violent rampage in a fairground, allegedly inspired by their hatred of travelling people, in 2016 and an attack on a hookah bar in 2013.
Mourain described the latter as "spontaneous" but Jérémie Crauser, one of the accused who has distanced himself from his former comrades, said the gang's leader ordered it as a "punitive expedition against people of immigrant origin".
In another assault in 2014 Cédric F, a member suspected of disloyalty, was stripped naked and beaten with a baseball bat, notably in the testicles.
Mourain was described as having set about the victim, pushing his thumbs in his eyes, biting him and licking his blood, Le Monde newspaper reports.
The second day was due to examine the paramilitary nature of the group and practises that included initiation rites and intimidation.