Black Trace

Black Trace also known as Demonic Butterfly Effect is a powerful mid-tier sacred gear. This is the third and final sacred gear that belongs to Annalise Blackwood, being the second of the two powerful sacred gears that was forcibly implanted to her by her father, Doctor Blackwood, a former scientist of the church who turned stray in order to create his "perfect creation" by using his own daughter and various church orphans as test subjects. The sacred gear initially belonged to Mia, a orphan girl of the church who was training to become an exorcist and nurse.

This sacred gear is a demonic sacred gear in nature, storing all the ill feelings and sins of it's former host. During her first fight, with Meguri and Ichiro, Annalise didn't use this sacred gear however during her second fight with Ichiro against the two exorcists of the church the sacred gear was used. She laters learns from Ichiro and Sona how to use the sacred gear to set traps, even using it with Ichiro's illusionary magic to increase it's capabilities.

Summary
Black Trace is shown to not have any special or unique origin, believed to have been made during the same time as Sword Birth. During the Great War, Black Trace was possessed by the descendant of Edward the Black Prince named Seleste who allied with Heaven. Seleste was one of the top 10 exorcists at the time. Despite using a demonic-type sacred gear she is regarded as a hero taught by the Church and even in Heaven to young angels.

The orphan named Mia, inspired by the former wielder of her sacred gear, Seleste, she wanted to use the abilities of this sacred gear in order to become a excellent exorcist and nurse in order to become a hero of the church. However her dreams were cut short when she was killed by Dr. Blackwood who implanted her sacred gear and soul inside his daughter.

Annalise later reveals that the reason she learned basic healing magic was as a tribute to what happened to Mia.

Appearance
Black Trace takes the appearance of a beautiful pair of pink and black butterfly wings that resemble the black swallowtail butterfly wings. The wings are shown to be as fragile as normal butterfly wings and as always take the shape of wings that fit their target perfectly.

Abilities
Being wing-type Black Trace allows its wielder to fly or glide by using the winds however the true power of Black Trace allows the wielder to [imprint] any attack, energy, curse, or ability that the wielder possesses onto any surface or object. They can then release it on command to serve as a trap or as a backup for other strategizes or attacks. Because of the demonic nature of this sacred gear, it adds a small amount of demonic energy to any attack the wielder launches.

Example: Annalise punches a wall [imprinting] the wall with her energy, she then releases the attack when a enemy is nearby causing a phantom-like hand made up of demonic energy including any energy she added to appear from the wall and punch the person closeby. Another example would be if Annalise were to add a explosive like magic to the wall when she releases explosive-type magic combined with demonic energy would burst from the wall.

The strength of the attacks are only equal to the amount of power she placed into the attack meaning the [echo] can't be stronger or weaker than her own attack or power. Due to the extra demonic energy added to the attacks, it can be fatal to holy creatures like angels or fallen angels.

Weakness
The wings are just as fragile as butterfly wings meaning it is easy to impale, cut or cause harm to the wings. If the wings are cut or harm they will heal however it takes time for this to occur and weakens the power of the sacred gear. Another drawback is the wings are very weak to holy attacks.

Trivia

 * I got the idea of the [echo] and [imprint] abilities of this sacred gear from Houki Minami who I brainstormed with.
 * The wing appearance of this sacred gear is from Accel World.