- Cristina Rosales: "It is unusual for a revolution to call for fewer rights for its people, not more."
- Zara Dearborn: "People... What people?"
- ―views of a member and a non-member, Lord of Shadows
In 2012, this faction of Shadowhunters pushed, through campaigns and demonstrations, to have all warlocks registered and to have internment camps for werewolves in order to keep Downworlders under control, mainly because they feared them and their power. The idea of the Registry was presented by their leader, Horace Dearborn, and became one of the primary causes of the group.
To have the power to propose the Registry as a Law, Horace had been hoping to take over the Los Angeles Institute from Arthur Blackthorn whose mental health was deteriorating; when Malcolm Fade killed Arthur, his death worked in favor of the Cohort.
The group attended the Council meeting where Annabel Blackthorn was to testify. They threw things at her and called her a monster and a liar, thus contributing to her going mad and killing Livvy Blackthorn and the Inquisitor Robert Lightwood. After the Inquisitor's death, Dearborn immediately took advantage of the other Shadowhunters' fears and was able to manipulate a group of Council members into electing him as the next Inquisitor.
One of the first things Horace did as Inquisitor was to send Emma Carstairs and Julian Blackthorn on a suicide mission to Faerie to retrieve the Black Volume of the Dead. He ordered a number of Cohort members, including Manuel Villalobos and Dane Larkspear, to follow and kill them once they'd retrieved the book. Also on Manuel's advice, Dearborn sent them to forge an alliance with the Unseelie Court. The mission resulted in Dane's death instead, though Horace still used it in his favor, blaming it on faeries to inspire fear and distrust to get more supporters.
Shortly after, a few members of the Cohort tortured and tried to kill Kieran, an Unseelie Prince, in the Hollow Place at the Scholomance. They arrested Diego Rosales, Divya Joshi, and Rayan Maduabuchi for helping the prince escape and imprisoned them in the Gard unfairly without a trial or even letting them speak on their behalf. To silence them, they used the Quietude rune on them while presenting them to the Clave.
Soon after, they passed the Registry without Consul Jia's consent during a meeting she was not aware of. A group led by Zara later followed her and Diana Wrayburn into Brocelind Forest and, witnessing their meeting with Gwyn ap Nudd, captured them for consorting with faeries. Jia's imprisonment allowed Horace to become the Clave's temporary leader while Jia was under investigation. The Iron Sisters released a statement that they rejected Horace's authority nor agreed with their ways and cut off communication with them.
The Cohort also made an alliance with the Unseelie King to spread the blight in Idris and kicked all the Downworlders out of Brocelind Forest. Because King Arawn was not easily manipulated, they conspired with Prince Oban to put him in power because he was easy to control. The plan succeeded, particularly after Kieran killed Arawn, and Oban was crowned the new Unseelie King.
Oban gave them an Eidolon demon and had it replace Oskar Lindquist so it could infiltrate the war council arranged by Julian Blackthorn in the Los Angeles Institute as a spy for them. They also set for the demon to later appear looking exactly like Annabel Blackthorn, down to the clothes she wore in the tragic Council meeting, to inspire fear among the Shadowhunters and further upset the Blackthorns.
Right after, Horace and Oban staged a parley on the Imperishable Fields that was Projected all across Alicante. They pretended to have just reached an agreement to end the war between the Unseelie Court and the Clave to make him seem like the best leader and convince Shadowhunters to join his cause. The farce and their failed attempt to kill Jace Herondale and Clary Fairchild was exposed by their arrival with Livia's Watch, and a battle between Shadowhunters and Downworlders against the members of the Cohort and the Unseelie faeries broke out.
Some members of the Cohort and their supporters who were inside Alicante tried to keep the Shadowhunters who wanted to fight in the battle locked inside the city under Horace's orders. However, the Silent Brothers finally renounced Dearborn's claim of leadership, proclaiming Jia the true Consul, and blew the doors open, slamming the Cohort members out of the way so that the protesting Shadowhunters could run to the Fields and join the battle.
Many members of the Cohort died on the battlefield, including Horace, who was killed by Julian when he and Emma turned into true Nephilim. The Cohort lost the battle and all the members who fought in it against their fellow Shadowhunters were imprisoned in the Gard where, tested with the Mortal Sword, they were forced to confess their crimes. They were considered responsible for Dane's death, for killing Oskar Lindquist, for using lies and intimidation to try and rule the Clave, for their false alliance with faeries, for imprisoning loyal Nephilim, and for nearly causing a civil war.
At a Council meeting, however, Jia chose to show mercy to the Cohort members and granted them a lenient punishment that would give them a chance to rejoin the Clave—being sent to different Institutes where they could redeem themselves before returning to Alicante. Jia also gave them the right to vote for their new Consul when she stepped down. Though many questioned this, Diana Wrayburn agreed, pointing out that the Cohort not being allowed to vote would give them the right to say that whoever was elected would not have been the majority's vote.
The Cohort nominated Lazlo Balogh as their representative. Despite their votes, Alec Lightwood won, and the Cohort still refused to recognize him. The other allies of the Cohort, including the guards surrounding them, revealed themselves and allowed the prisoners to arm themselves. They threatened to commit mass suicide if they did not surrender Idris to the Cohort; to prove that they weren't bluffing, they had Amelia Overbeck kill herself in front of the audience.
They demanded that all non-supporters leave Alicante forever, with the promise to ward the city heavily so no one could get in or out, transforming Alicante into both a prison and a fortress. So they would not kill themselves, Alec accepted their terms and the Clave split; the Cohort and their followers stayed in Idris and all the others left their homeland, which resulted in the creation of the Clave-in-Exile.
Upon this division, a portion of the Shadowhunter population stayed in Idris to be ruled by the Cohort, and the rest left, though there were also some Cohort members who chose to leave Idris and supposedly abandon the Cohort to be with their families, such as Paige Ashdown. The Cohort members and supporters who stayed in Idris were left isolated within their wards, with no access to the outside world, to the Mortal Instruments except Lake Lyn, and to the Silent Brothers and Iron Sisters who renounced their rule.
Associates (unconfirmed members):
- Apparently about a third of the Shadowhunter population stayed in Idris after the split.
- In The Lost World, more information about what was going on with the Cohort in Idris at the time of the story was revealed.
- According to Cassandra Clare, the Cohort, due to their self-imposed isolation and lack of access to new weapons, healers, and the outside world with demons, will no longer be able to perform the duties of typical Shadowhunters, having essentially abandoned their mandate from Raziel because they care more about power and the ideal of purity they created. Their plans are very different from what we have seen Shadowhunters do before and won't be good for Downworlders, the Clave-in-Exile, nor mundanes. This will be explored further in The Wicked Powers.