Miria was secretly investigating the Organization after she swore revenge against it. These both stem from an Awakened Being hunt, when she discovered that the target was originally a close friend, Hilda, who had awakened. The shock of this led her to nearly awaken herself. Miria was first introduced in Volume 5, Scene 25 as a team leader of an Awakened Being Hunting Squad where she had an uneasy encounter with Clare due to the latter's disobedience. She was assigned again as leader of an Awakened Being hunting squad - formed of Clare, Helen, and Deneve. The squad was almost defeated but Clare and Miria eventually killed the male Awakened Being. After realizing that they had had almost no chance of surviving the fight, Miria believed that her squad had been betrayed by the organization and sent on a suicide mission. Her theory was that her squad, composed of partially-Awakened Claymores, were considered troublemakers by the organization. After the battle, she told Clare, Helen, and Deneve that she'd found one of the organization's darkest secrets, but didn't reveal it out of fear for the others' safeties. She told them to keep a low profile and stamp out their trouble making images, and that she'd contact them when the time was right.
The Northern Campaign
Miria was the chief Claymore in the Northern Campaign, due to her having the highest rank. She demonstrated her tactical skills by the way she organized the Claymores into small teams that would allow them to gain experience in fighting with Awakened Ones with minimal loss of life. In the first fight against three male Awakened Ones, her strategic capabilities were even recognized by one of the Awakened Ones. Miria directly led the following Claymores: Queenie (#20), Tabitha (#31) and Yuma (#40). It was her planning that enabled some of the Claymores in the campaign to survive. In addition, her own team took only one fatality. She was the only captain to survive the second battle.
Seven Year Time-Skip
While in seclusion she develops a new way to greatly increase her normal speed, without needing the yoki bursts. Deneve describes the technique as "A new kind of Mirage" and although it's slightly slower than her former technique, this is actually considered superior because there are no limits to how many times she can use this ability, as opposed to the short yoki bursts needed for her mirages. With this new technique she's also able to achieve more precise movements. She serves as the leader of the surviving Claymores, who are Clare, Helen, Deneve, Tabitha, Cynthia and Yuma. Miria recently revealed that she had accessed the Organization's archives prior to the Northern Campaign. She discovered shocking information, but it has taken her seven years to piece everything together. She reveals her theory that the Yoma are not natural, and that she believes the Organization created them. That the lands they live in is actually a massive island that the Organization is using to conduct experiments towards the creation of an ultimate weapon to win a war between two great nations in a distant land that has been raging for over a hundred years. These ultimate weapons are the Awakened Beings. She has decided to let her comrades leave Rabona to finish whatever tasks they might have. She is currently staying in Rabona with Tabitha.
Rebellion against the Organization
Powers and Abilities
Like all Claymore's Maria possesses strength, speed,durability and regeneration the far exceeds that of a normal human. Maria is so fast that she uses a technique called that "Phantom Mirage" allows her to leave several ghost like afterimages behind which she uses to confuse opponents.Maria has moved so fast that rain drops seem to be standing still relative to her,she has also move faster then the human eye or other Claymore's eye's can follow.Maria also has super strength that allows her to cut through steel and stone alike with moderate effort.With her vast regeneration she has been able to heal from fatal wounds and lost of limbs in a relevantly short spans of time.