O'Brien

O'Brien is a S.H.I.E.L.D. agent who worked with Phil Coulson and Melinda May during a mission to capture an Inhuman, during which O'Brien and his team were briefly brainwashed. After the capture of Robert Gonzales S.H.I.E.L.D. base, he was sent to monitor the agent Fitz who expressed a desire to leave S.H.I.E.L.D.. Later he assisted in the attempted killing of Hive. However O'Brien was later caught in a trap and transformed into one of the Primitives with a bomb containing poisoned Terrigen Mist.

Hunting Inhumans
Agent O'Brien was assigned to the case of Eva Belyakov, a gifted individual and Index candidate who was to be evaluated and taken in by S.H.I.E.L.D. before a different government agency could. He traveled to Bahrain under the command of Agent Hart and with Agents Phil Coulson and Melinda May brought in to help.

O'Brien watched Coulson try to reason with Belyakov and was instructed to make sure a group of locals, who had been put under the coercion of Eva Belyakov's daughter, Katya, did not interfere with the mission. Eva Belyakov caused a large commotion which resulted in O'Brien and the Bahraini men pulling guns out at each other. One man grabbed Katya Belyakov, so O'Brien went with the thugs so the girl would not be hurt. O'Brien became part of Katya's thrall, and answered Coulson's phone call simply telling him to leave them alone.

The rest of the S.H.I.E.L.D. team that went in were put under Katya's power, and O'Brien fought Melinda May with them. They were brought into a room by Katya following the death of her mother, where May shot the girl before she could kill O'Brien and the other agents and brought them out of her trance. O'Brien could not remember any of the events from when he was under Katya's spell, he only remembered seeing all of the dead men on the floor when he came to, starting rumors about the infamous tale of May's nickname, "The Cavalry".

Battle Against Hive
To be added

Becoming a Primitive
To be added

Allies

 * S.H.I.E.L.D. (First Incarnation)
 * Nick Fury - Director
 * Phil Coulson - Colleague
 * Melinda May - Colleague
 * Hart - Colleague
 * Hive † - Enemy turned Enthraller

Enemies

 * Eva Belyakov †
 * Katya Belyakov † - Former Enthraller
 * Kree Reapers
 * S.H.I.E.L.D. (Second Incarnation) - Allies turned Enemies under Coercion
 * Phil Coulson - Director
 * Melinda May - Colleague
 * Alphonso Mackenzie - Colleague
 * Anderson - Colleague
 * Piper - Colleague
 * Leo Fitz - Colleague