Kingdom Hearts Birth by Sleep
Right after Terra slays an Unversed with Aqua and Ventus, Braig confronts him at the Radiant Garden Aqueduct, informing him of his capture of Master Xehanort. However, Terra is disbelieving of Braig's claim as Master Xehanort is a seasoned Keyblade wielder and magic user. Baiting Terra to come see for himself, Braig informs him that Xehanort is being held in the Purification Facility under the Outer Gardens and that he might want to hurry before he loses his patience. Terra does arrive later to find Master Xehanort chained to a large pipe, to his horror. Braig then enters, telling Terra that he was told all about the Keyblade by Master Xehanort and the things it can do. Deciding that he wants a new "toy" to use instead of his arrowguns, Braig wished to obtain a Keyblade of his own. However, Terra informs him that Keyblades are picky about their wielders as it takes the right heart to even simply touch one. Braig then lies that he'll kill Master Xehanrot if Terra coems any closer to him. However, Master Xehanort tells Terra to fight back as it would shame Master Eraqus and his fellow disciples, prompting Terra to go againsy his better judgement. Despite using his teleportation abilities to the fullest, Braig ended up the loser of their fight as Terra succumbs to darkness and uses to energy shots from his Keyblade that permanently damage Braig's right eye and another scars his left cheek before breacking the chains holding Xehanort to the pipe. Full of pain, Braig retreats to Hollow Bastion to be treated for his injuries.
However, it later turns out that Braig was working with Master Xehanort. Angered greatly at the loss of his right eye and scarring on his face, Braig attempts to shoot Master Xehanort from behind, claiming that Xehanort said he wouldn't get hurt, but Master Xehanort threatens him into backing down and continuing with their plan to make Terra succumb to the darkness. Braig agrees to this as he is still needed to assist in this and that he was promised a Keyblade to wield himself.
He later appears in the Keyblade Graveyard having allowed Master Xehanort to place a fragment of his heart within him, indicated by his remaining eye becoming yellow, and his ears becoming pointed. He appears in front of Aqua and Ventus, attempting to get them to attack Terra and kill him for his role in the death of Eraqus, but they refuse to forsake their friend. After paying particular attention to and mocking the angry glare Ventus gives him, Aqua battles Braig for trying to turn them against their friend and defeats him. He begins to escape, and Aqua chases after him, but she realizes that she can't leave Ven in his fragile state alone, so she stops and allows Braig to return to Radiant Garden.
Later, back at the Radiant Garden, Braig leads Dilan and Ansem to an amnesiac young Xehanort, the result of Master Xehanort possessing Terra's body, and smiles discreetly but triumphantly to himself, relieved that his friend's plan worked.
However, Braig later approaches the new Xehanort, now an apprentice under Ansem, and is dismayed to find that the new Xehanort does not recognize him, and Braig's attempts to help Xehanort remember prove only to annoy him. Braig, at one point, questions if this new Xehanort is actually Terra, but Xehanort still does not respond, much to Braig's relief. Braig nevertheless says in a friendly manner that he's got Xehanort's back.
Between Kingdom Hearts Birth by Sleep and Kingdom Hearts 358/2 Days
Braig became one of six apprentices to Ansem the Wise, the ruler and scientist of Radiant Garden, alongside Dilan, Even, Aeleus, Ienzo, and Xehanort. After Ansem began performing tests on Xehanort's heart, Braig convinces the other apprentices to aid him and Xehanort in conducting inhumane experiments on the human heart and the darkness within it. Such experimentation led to the mass creation of Heartless. Ansem quickly discovered their secret experiments, and immediately ordered them to stop. One day, after being advised to review their research data by King Mickey, Ansem found that the effects of their experiments had become irreversible.
Eventually, Braig found Xehanort had unlocked the hearts of Dilan, Even, Aeleus, Ienzo, Isa and Lea. When questioning him about whether or not he has regained his memories, Braig has his heart unlocked and fades into darkness. However, his strong will allowed him to continue as a Nobody called Xigbar.