Children of Gabriel

The Children of Gabriel is a mysterious, cult-like militant group in conflict with the Sanctum Citizens. They are interested in killing the Primes.

History
The Children of Gabriel was founded sometime after the Mission Team Alpha landed on Sanctum. They became a cult-like rebel militia group. The group was founded by their leader, Gabriel Santiago, who is also known as the Old Man.

In The Children of Gabriel, they successfully raided the Gagarin and stole guns from the ship. They beheaded the corpses of the three Primes, Victor, Faye, and Daniel, that were killed on Eligius IV and took the heads with them. They successfully infiltrated the Sanctum settlement and attempted to kidnap two Hosts, Delilah and Rose. Clarke Griffin with Sanctum guards were able to successfully recover Delilah, but another abductor got away with Rose. Outside the perimeter, they successfully captured Octavia Blake after she tried to attack them.

In The Face Behind the Glass, the Children of Gabriel are torturing Octavia for information about any other Royal Blood they might have had on the ship besides Clarke. However, Octavia refuses to comply. Tosh suggests killing Octavia and Rose but Xavier disagrees with her. Tosh argues that the most important thing is stopping the Primes from getting another host. On the other hand, Xavier wants them to take the royal blood child (Rose) and the Earth girl (Octavia) to impress "the old man." To help settle the argument, Tosh and Xavier meet up with more members. While the Children of Gabriel are arguing among themselves, Octavia manages to escape with Rose. The Children of Gabriel run after them and apprehend them. Luckily, Diyoza arrives and shoots them all. Tosh fakes being dead, waiting for her chance to attack. While Octavia is double-checking to confirm they're all dead, Tosh gets up and kills Rose. Octavia then kills Tosh instantly. After that, Octavia and Diyoza team up to go hunt and kill the remaining Children of Gabriel, along with their "old man."

In Memento Mori, Xavier reveals to Diyoza that the Children of Gabriel was founded by a Gabriel Santiago, after he lost his stomach for immortality. So, Gabriel became the group's leader to kill the Primes after a "Moral Awakening."

In Nevermind, while exploring Josephine Prime's memories, Clarke discovered that in the past, Isaac, the lover of Kaylee Prime, saved several Null infants by secretly giving them to Gabriel after they were left in the Offering Grove to die. Oblation was instated by Josephine to get rid of those lacking the black blood gene to prevent those Nulls from further "muddying" the bloodline and diminishes the chance of Hosts being born.

In The Old Man and the Anomaly, Charmaine Diyoza discovers that Xavier is in fact Gabriel Santiago himself in a new host. Gabriel explains that after leaving Sanctum, he had no one to remove his Mind Drive until he met someone named Eduardo who became like a son to him. By the time Gabriel was ready to die, the real Xavier was born, a Nightblood who was born free. Thinking that Xavier would make the perfect host for Gabriel without moral concerns, Eduardo wiped Xavier's mind and used him to resurrect Gabriel who subsequently killed Eduardo in anger. Rather than reveal himself to his followers, Gabriel chose to hide amongst them as Xavier. As a result, none of the Children of Gabriel know that their founder is still alive and think that he abandoned them.

Society
The Children of Gabriel is a cult-like militia group. They serve a mysterious figure known as the Old Man – who is actually their founder, Gabriel Santiago, the former thirteenth Prime, referred to as the demon Gabriel by the Sanctum Citizens. None are aware that Gabriel is in fact still alive and hiding amongst them in the host of Xavier after Gabriel was unwillingly resurrected following his last death.

Their goal seems to be to kill all the Primes. After beheading corpses of three Primes, the group chants "Death to Primes!", over and over. They also want to kidnap, and possibly kill, any Hosts, that is, those having the Royal Blood and thus potential to be future Primes. In order to do this, they patrol the radiation shield and look for opportunities to get inside and to watch out for any Primes walking out. The Sanctum Citizens are aware of them and use the radiation shield to keep them and other dangers out.

The Children of Gabriel know a lot about Sanctum plants. They use the forest as their weapon, like Xavier did by spraying Octavia with spores.

Notes and Trivia

 * The group has some similarities with Grounders. They hide in the woods, wear camouflage clothes, and are in conflict with a more technologically advanced society.
 * The credits at the end of the episodes and the characters themselves, referred to the Children of Gabriel as terrorists.