Ν-No.13-

""Hahahahaha! Ragnaaaaa! Ragna! Ragna! It's impossible, Ragna! Nothing will change! You can't change anything! Hahahahahaha!""

ν-No.13-, more commonly abbreviated as Nu-13, and also known as the Sword of Hades, is a Boundary Interface Prime Field Device who is modelled after Saya and lusted after Ragna the Bloodedge, hoping to fuse with him to become the Black Beast.

Nu first appeared in BlazBlue: Calamity Trigger, and was absent for BlazBlue: Continuum Shift only appearing as Lambda's Unlimited Form. She reappeared in BlazBlue: Chrono Phantasma onward.

Personality
"Although she judges situations mechanically, she will occasionally show moments of intense emotion. She has the highest-priority objective to "be together with Ragna" and towards Ragna alone will act girlishly."

To almost everyone, Nu is cold, mechanical, and apathetic. She is solely focused on her mission to fuse with Ragna, and will not allow anyone to come between her and that objective. When away from Ragna, Nu's speech pattern is robotic, using complicated and professional language, and vocally exclaiming when she is loading or commencing the extermination of a target. Like this, she will often analysis her opponents and assign them warnings, coldly assessing their strengths from a glance.

But to Ragna, everything changes. When around him, Nu is filled with emotion, lusting after him and breaking her mechanical language. She will vocally call out to him with sexual innuendo, taunt him about his darker feelings, and threaten to kill him, all while baring a smile filled with glee. It appears her feelings of "love" towards him are genuine, but love to Nu is simply fusing with Ragna to become the Black Beast - nothing more or less. She won't allow anyone else to touch him, she only wants the Grim Reaper to herself, and as far as she is concerned, everyone else is an obstacle in the way of her happiness.

Eventually, Nu's mechanical expressions faded away, and she is nearly always filled with intense emotions, particularly on killing others and seeking Ragna. She went insane from not being with him, and would do quite literally anything to become one with him. She would even defy the orders of those who command her, being derogatory and showing a sharp tongue to anyone who isn't her love.

Nu has no hobbies, bar thinking about Ragna. Nu is part of the yandere trope of characters that appear in Japanese media.

an evil sign
Now in a laboratory, Nu was connected to several cords, including one large one in her eye, each injecting seithr into her body. Scientists meddled with constantly raised the levels during the process of this. Nu's body began to spasm as she came to life, and the scientists declared that their job was complete. They decided on the schedule for her to be delivered to Relius Clover, while discussing how she was made by both him and Sector Seven. However, they were interrupted in their discussions by Hazama, who claimed to have an order from the Imperator to pick Nu up personally. Hazama asked to see the unit for himself, which the lead scientist agreed to. He took Hazama to the chamber she was contained in. He touched her and marvelled at their work, proclaiming that she truly was the thirteenth unit. However, after the scientist left, he began to mock Nu, demanding she wake up. Her eyelids began to flutter in response to his words.

Calamity Trigger
"A young girl who appeared from the "Cauldron" buried deep within Kagutsuchi. Nothing about her appearance suggests who she may be."

When Noel Vermillion came into the presence of the cauldron inside Kagutsuchi, Nu descended from it. She immediately identified Noel as the twelfth unit, the long missing Mu-12. She equipped Murakumo and battled against Noel and her Arcus Diabolus: Bolverk. Eventually, the fight ended with Nu victorious, ready to kill her predecessor; the conclusion was better than she could have hoped for, as Ragna lept in front of the blade meant to kill Noel. Nu, ecstatic that Ragna had finally arrived, began to tell him all about her dreams of seeing him, and ripped her blades out of him. The two battled, and again, Nu emerged victorious. She stabbed him again, and told Ragna about how much she wanted to stay by his side. The pair began to fall into the cauldron, to become a Black Beast, but Noel managed to barely save Ragna with an outstretched hand, and Nu fell into the cauldron to die alone.

Though she had died, there was a small duration where Nu's soul had yet to reach the Azure. Kokonoe snapped up the soul and put it into Lambda-11, Nu's sister unit. Nu's memories were sealed away, but she was able to see Ragna one more time before Lambda herself died. As Nu has a life-link with Ragna, she began to reconstruct herself in the Boundary shortly afterwards.

Chrono Phantasma
"Nu-13, who resurrected by her own will in order to fuse with Ragna. Hazama calls her the "Sword of Hades." Rebuilt by Hazama, she once again stands before Ragna."

Central Fiction
"A young girl who appeared from the "Cauldron" buried deep within Kagutsuchi. She is a Boundary Interface Prime Field Device fitted with the Phenomenon Weapon "Lux Sanctus: Murakumo." She has appeared once again in order to fuse with Ragna, but things seem a little different from before."

Cast into the Embryo, Nu’s memories were changed so that she believed it was 12/31/2199. She also became one of the chosen. She woke up in Kagutsuchi near the cauldron, being awoken by Noel. Despite being knocked to the floor, she continued her assault, only being stopped by Ragna. She lost to him, something she didn’t think possible, but instead of killing her, the Grim Reaper offered to save her, only being unable to as he was teleported away by Nine the Phantom. She was transported to Ikaruga and told by Nine to kill Izanami so she could claim her piece of the Azure and have her wishes come true. Relius had also ordered her to start hunting for the Nox Nyctores’ and began with the Arma Reboare: Muchourin, finding Platinum the Trinity but being able to keep track of her due to the latter’s fluctuating existence.

She later found Bang Shishigami, the wielder of the Phoenix: Rettenjo and began fighting him until she was interrupted by Nine. She fought back against both, insanely muttering that the Nox was hers and hers alone; despite this, Bang still managed to flee. While searching for the ninja, she was attacked by Arakune who wanted her Murakumo. She was saved by Relius, who conducted repairs on her, and she allowed it. Nu later followed Izanami into Nine’s workshop and nearly assaulted the witch had she not been stopped by Jubei. The two fought until the Corpus Sepulcro: Requiem froze the area in space-time.

When Nu awoke, she was still fighting Jubei, although this time above ground and near the Amaterasu Unit. Intent on destroying it, she fought Jubei and then eventually both Hakumen and Izayoi. She beat the both of them, only being stopped by Ragna, who she revealed to that she had absorbed the core of Gigant: Take-Mikazuchi. When defeated, Nu was knocked unconscious but was forced to awaken by Terumi who sent her insane and broke her soul. Nu lashed out, nearly killing Tsubaki, a blow that was defended by Hakumen – she fought the leader of the Six Heroes, being not only defeated, but knocked unconscious. She was watched over by Tsubaki and Jubei until all three of them dissolved into seithr.

In the new world created by Ragna, Nu was left in a catatonic state. She now lives bedridden inside a church with Noel and Lambda as her carers.

ν-No.13-
''A young girl who appeared from the cauldron buried deep within Kagutsuchi.

''She is one of the three sacred units, the Murakumo Unit. She is both the last Nox Nyctores, and the core of a Black Beast. Her actions and personality is machine-like and because of Saya’s soul, she shows emotion while in the proximity of Ragna.

''She’s also a fragment of the Black Beast’s shell, which houses Ragna, and by fusing with him, they become the Black Beast that brought terror to the world. She’s also known as the 13th Prime Field Deice, or the Blade of Hades.

''Although she fell into the cauldron once, she was revived as Lambda, after being retrieved by Kokonoe.

''Now she roams as the Blade of Hades, in hopes that she might fuse with Ragna once more. All according to Hazama’s plan…

''Fusing with Noel, Nu gains the power of the Successor to the Azure, bringing down the Amaterasu Unit to the realm of mortals.

Sword of Hades
''Hazama refers to Nu by this name as she’s being smelted in her Cauldron, at the end of the story of ‘Continuum Shift.’