Luciela

Luciela was Claymore #1 during the same generation her sister, Rafaela, was #2. She later awakened and became known as the Abyssal One of the South before becoming merged with her sister.

Appearance
human form: 

Luciela has the appearance of a young girl, presumably the appearance she had when she awoken. She has long hair which she wears in bunches, much like Dietrich's. She wears a long dress with lots of ruffles in her first appearance in the manga.

awakened form:

In her awakened state, she is a large humanoid with feline hindlegs. Her head resembles that of a cat and has two gaping jaws, one atop the other. In battle, Luciela uses her foreclaws and the two long, muscular tails extending from her hindquarters. Her tails sport multiple fanged mouths along their length, and Luciela can manifest similar mouths anywhere upon her person.

As a combined Awakened Being she resembles the Clare and Teresa statue. A large halo-like structure can be formed from the opened mouths of the two faces. But that form is just a decoration. As the destroyer she is a black mass of yoma and possibly other beings it has destroyed/assimalated.

As a Claymore
Luciela became a Claymore at the same time as her sister Rafaela. This was a time when Teresa was still a child. The Organization used her and her sister in a "Soul Link" experiment. The experiment failed when Rafaela was unable to pull her sister back form her awakened state, causing Luciela to completely awaken. Her awakening was disastrous and drove the Organization to the brink of ruin, as it took place in the Organization's headquarters. Alicia and Beth are a successful product of this technique; it was said that the project only worked with identical twins, which Luciela and Rafaela were not. She left the headquarters and eventually became the Abyssal one of the South.

Fight with Isley
She lived in the Southern Territory, presumably alone, until Isley of the North came to invade her territory. Luciela and Isley began to duel over Luciela's territory, which ultimately led to her defeat. She retreated after losing all of her Yoki. Injured, she reverted back to human form and eventually came across Rafaela. Wanting to finish off Isley, she embraced her sister, and pleaded for her to Awaken and align with her. But Rafaela broke her weakened sister's back, apparently killing the latter.

After Seven Years
Seven years later Luciela and Rafaela's bodies have merged together and are in the possession of Riful, who is wishing to awaken them into a much more powerful being. However, she isn't able to do so on her own, and ultimately captures and enlists the help of the Claymore Renee. Renee is able to stir the merged being, but it is ultimately Clare's presence that awakens the merged sisters. Clare meets with Rafaela inside her mind and recieves all of her memories before Rafaela's consciousness dies. This is what ultimately awakens the sisters.

As a Combined Awakened Being
When Clare escapes Rafaela's mind she is standing in front of the new Awakened Being. A large halo-like structure appears and fires many large rods off into the surrounding areas, piercing through Riful and Dauf and one impaling Beth in the stomach. The rods start to change and the take the form of cat-like creatures, resembling Luciela's awakened form.

They are seen attacking Clare, Helen and Deneve shortly after. The creatures are seen losing limbs and one even gets decapitated but they continue to fight on. They are seen firing rods much like Dauf, which allow them to regenerate when they impale a living creature, making them parasites. According to Clare the creatures will only cease to function when they expend all their energy fulfilling their destructive nature. The best way to stop them is slice them into as many pieces as possible to prevent them from moving, although they can still fire projectiles. After all the creatures have been defeated, she prepares to release more.

Fight With Priscilla
While Helen and Deneve running to the destroyer to hope to lose track of Priscilla, Helen launches her Claymore as a diversion to get the destroyer to attack.Priscilla is struck by the rods of the destroyer and traces the rod to the main source.With Priscilla's nails wrapping around the entire structure, rips off the destroyer's outer shell.Revealing that the destroyer is actually a black blob of zombies.Helen notices that everything it touches turns corrupted and dies.Deneve states that it drains the life energy of everything it touches and Helen,unknowingly, notices Clare is missing. Clare had been struck by the deadly rods of the destroyer and is now breaking apart. Priscilla turns to confront the destroyer, going to the middle where she senses the most energy. Priscilla then confronts the destroyer with ALL of her power.