The Messengers, or The Twelve, are a group of twelve individuals with ties to the Army of the 12 Monkeys. Armed with knives made of bone, the mission of the Messengers is to paradox Primaries in various time periods to collapse time.
The Messengers were born in 2015. They were genetically modified and created by the Army of the 12 Monkeys using the DNA of Olivia as a model. Olivia was developed in the late 1950s by a German doctor named Kirschner. The doctor used the DNA of Mantis, Olivia's so-called "Mother." Because Mantis was also designed in 2015 after Olivia before being sent back in time, it is a closed time loop.
The Messengers are first seen wearing dark cloaks and covering their bodies in ash. Before traveling through time, the ash is wiped away. They carry knives made of bone from respective Primaries. Each knife is used to kill the Primary from which it came, causing temporal paradoxes that unravel the fabric of time. The six Messengers that are sent back in time are sent in pairs to various time periods to kill the Primaries.
Mantis and a male Messenger arrive in 1944 from 2043. They kill and impersonate a married couple in order
to find their target, Thomas Crawford. Mantis seduces Crawford and then kills him in ritual fashion with a bone knife, but to their dismay, the expected result does not occur. The Messengers soon learn that they are looking for another man with the same name--Crawford's son, Tommy Jr. They go to the mental institution where Tommy is a patient; there, they run into Cole and Railly, who have found Tommy first. Railly kills the male Messenger, but Mantis kidnaps Cole and tortures him with electroshock to make Railly give up Tommy to her. She performs the ritual again and kills Tommy with the bone knife (carved from Tommy's own breastbone), causing a temporal paradox that knocks her out.
One of the Messengers, Charlie, arrives at some point in the 1950s from 2043. By 1957, he had killed the
other Messenger he traveled back with and married their target, the final Primary. Cassie and Cole confront him as he is about to paradox his wife. Initially reluctant to kill and paradox his wife, he ultimately does so at her own request so that they can be together in the Red Forest. The resulting paradox is said to be the final straw that will collapse time.
Later, Cole projects his mind back to 1957 and changes the timeline, killing Charlie before he can paradox his wife. This foils the Messengers' mission.
Mantis resurfaces in Germany, where Cole, Cassie, and Ramse, are hunting down a lead to Titan. Dr. Kirschner takes the team to his lab, where Olivia is being raised in a windowless room. The Army of the 12 Monkeys kills Kirschner before he can reveal any more information. Mantis takes Olivia to her home in Virginia, where she will raise her alongside the Pallid Man.
Mantis dies with her son, the Pallid Man, at her side.
Two Messengers arrive in 1975 from 2043 to kill the Primary Kyle Slade. One of the Messengers is captured by Slade, who believes him to be The Witness. The other Messenger follows Ramse to the Emerson Hotel, where Ramse emerges victorious in a fight to the death. The other Messenger, as well as Slade, are killed in the warehouse without a paradox occurring.
The Twelve are born in 2015. Olivia oversees their delivery and speaks of the role they will play in the next cycle of the 12 Monkeys' plans.
The Messengers recruit Deacon to break them into the Temporal Facility. They cover themselves with ash and wear long, dark cloaks. Their leader claims that what is inside the facility is of great interest to them and wants reassurance from Deacon that their break-in will be successful.
The Twelve successfully invade the facility. They take Jones into custody and express their desire to commandeer the time machine. Their leader assures Deacon that once they make use of the machine, the temporal facility will be Deacon's for the taking. Their plan begins to unravel when Cassie unexpectedly arrives in 2043 by way of the time machine.
Their attempt at hijacking the machine is ultimately thwarted by Jones, Cassie, Whitley, and Deacon, who turns his back on them. Six of The Messengers are sent back to various points in time, while the remaining six are killed.