Dark Fragment

Yuuno (right) and his Dark Fragment (left) in Gears of Destiny

Dark Fragments (闇の欠片 Yami no Kakera, also referred as "Dark Pieces") are fragments of Darkness of the Book of Darkness and the the primary opponents during the Dark Fragment incident, as shown in Magical Girl Lyrical Nanoha A's Portable: The Battle of Aces. Dark Fragments are regrets and strong desires brought to life from the memories of those who interacted with it, to bring to life individuals from from memories, so that even those who have not interacted with the Book of Darkness personally can be brought back as long as those who knew them had. This was made possible by Nanoha and Fate refusal to seal Reinforce, allowing the Defense Program to recover enough power to spawn Dark Fragments. The fragments tend to go away dissolve once their regret or strong desire is solved one way or another. The Dark Fragments are capable of merging into the Defense Program's Materials including the Defense Program itself(which takes the form of a new Will of the Book of Darkness in Nanoha, Chrono and Reinforce's routes).

Appearance and personality

Fate (left) confronting her Dark Fragment doppelganger (right)

These dark pieces' appearance is characterized by their slightly off (in The Battle of Aces) or darker (in Gears of Destiny) color scheme compared to the real person. They usually (with three notable exceptions that being Dark Fragment Fate from Reinforce's route, Dark Fragment Signum from Chrono's route and Dark Fragment Shamal from Signum's route) have no awareness that they are fabricated, and the Defense Program only implants partial memories of the original into them up to the point in time of the notable regret or strong desire chosen by the Darkness(with the Dark Fragment of Fate faced by Reinforce being the one Dark Fragment possessing almost all of the original's memories even up to the Dark Fragment incident itself). With two notable exceptions, all Dark Fragments believe they are at their lowest and hardest point in life:

• Yuuno (fought in Shamal's route in Gears of Destiny): just before meeting Nanoha
• Nanoha (fought in Vita's route): during her second battle against the Wolkenritter; Nanoha (fought in Signum's route): when starting out as a Mage; Nanoha (fought in Shamal's route): Following her first battle with the Wolkenritter;
• Fate (fought in Vita's route): During the Jewel Seed Incident; Fate (fought in both Fate & Chrono's route): after the Jewel Seed incident; Fate (fought in Reinforce's route): Following Nanoha's battle with Levi (due to mistakenly assuming Levi was a Dark Fragment of herself)
• Chrono (fought in Hayate, Shamal and Vita's route): Sometime after his father's death. Chrono (fought in Chrono's route): Sometime before he reached the age and appearance he had during the Jewel Seed incident;
• Levi (fought in Dearche's route in Gears of Destiny): During her time "half-asleep"; Levi (fought in Signum's route in Gears of Destiny): Shortly before reviving in Gears of Destiny
• Vita (fought in Zafira's route): When she entered the Depression Stage of Grief over people dying around her during her service under previous masters; Vita (fought in Shamal's route): When she entered the Anger Stage of Grief over people dying around her; Vita (during Nanoha and Chrono's route): During one of the Book of Darkness incidents that took place following the creation of the TSAB; Vita (during Vita, Hayate, Signum and Reinforce's route): When she acclimated to her life as a Guardian Knight
• Signum (fought in Nanoha's route): During one of the Book of Darkness incidents that took place following the creation of the TSAB; Signum (fought in Hayate's route): Following Hayate's hospitalization; Signum (fought in Vita's route): During one of the previous Book of Darkness incidents; Signum (fought in Zafira and Reinforce's route): During the first Book of Darkness incident where she first segmented off from Dearche; Signum (fought in Chrono's route): When she was absorbed into the Book of Darkness because of the Liese Twins;
• Reinforce/Will of the Book of Darkness (fought in Shamal and Zafira's route): During one of the previous times the Book of Darkness existed(the Dark Fragment faced by Zafira even lacks enough of the Defense Program and Recovery System to notice despite lacking memories of the Defense Program's removal). Reinforce's Dark Fragment is identical to the resurrected Defense Program(which has become the new Will of the Book of Darkness) in that she has purple battle armor instead of Reinforce's blue;
• Zafira (fought in Signum, Zafira and Reinforce's route): When he first segmented off of Dearche when he was still a beast; Zafira (fought in Fate's route): Right after one of his masters was harmed at some point. Zafira (fought in Nanoha's route): During one of the Book of Darkness incidents that took place following the creation of the TSAB; Zafira (fought in Shamal's route): During one of the Book of Darkness routes;
• Shamal (fought in Nanoha's route): Following an incident where the other Wolkenritter were defeated; Shamal (fought in Hayate's route): When she first segmented off of Dearche during the first Book of Darkness incident before learning of the Will of the Book of Darkness's existence; Shamal (fought in Fate's route): During a previous Book of Darkness Incident when seeking a Fate lookalike(presumably Alicia) in order to claim her Linker Core(possibly explaining Alicia dying while Precia survived the reactor accident); Shamal (fought in Signum's route): During the Dark Fragment incident itself; Shamal (fought in Chrono's route): During the last Book of Darkness incident;
• Hayate (fought in Fate's route): immediately after the Wolkenritter are murdered

While none of them except Dark Fragment Fate (namely the one born from Fate watching Nanoha's battle with Levi), Dark Fragment Signum and Dark Fragment Shamal are aware they are serving the Darkness, all find some excuse to attack the player character due to the dark moment they were pulled from. The only exceptions are the Dark Fragment versions of Hayate (all but one of them), whom Nanoha, Chrono and Signum encounter on their routes in The Battle of Aces and the Dark Fragment version of Signum whom Fate encounters in her route in The Battle of the Aces, all of whom (except the Hayate encountered by Chrono as her strong desires involve a dream rather than combat) are so eager to have a mock fight against their opponents, that they will happily ignore all of Nanoha, Fate and Signum's attempts to avoid violence.

Relation to Materials

The Materials(which are formed from Dark Fragments merging together) are not the same as the Dark Fragments they are formed from since they are have their own personalities distinct even from the rare Dark Fragments who are fully aware of who they are, who they are working for, and what they are doing, although according to the Levi's own statement, she was "half-asleep" during most of it(and Stern felt unexplainable feelings of bloodlust during her first battle against Nanoha). This half-asleep state likely results from absorbing each other's Dark Fragments alongside a majority of their own(with Levi absorbing Stern's and Stern absorbing Levi's with Dearche being the only one to have not entered a half-asleep state). Unlike Dark Fragments of the Nanoha, Fate, and Hayate, Materials have their own distinct personalities and different designs from their respective originals. In Gears of Destiny, Levi, Stern and Dearche having fully reconstructed themselves without each other's data and no longer need to create Dark Fragments(with any being created being a mere side effect caused by being connected to the Defense System) yet System U-D still creates other Dark Fragments in order to revive the last of the 4 Materials: the Defense Program itself.

Side Effects from battling the Wolkenritter

Whenever a Wolkenritter(and possibly Reinforce herself) fights a Dark Fragment the Defense System's data gets lodged in them. While there was a slight possibility that the Defense System might take over their programing they managed to defeat all their Dark Fragment opponents and survive the Dark Fragment incident and System U-D incident without gaining any of the Defense System's bloodlust(no info on whether or not their devices gained bloodlust resulting from the battle).