Livia Blackthorn

Livia Blackthorn is the twin sister of Tiberius Blackthorn, as well as the sister of Jas, Jules, Dru, and Tavvy, and the half-sister of Helen and Mark. She lives at the Los Angeles Institute with her siblings, under the guardianship of their uncle, Arthur.

History
Livvy was born into the Blackthorn family to Andrew and Eleanor Blackthorn in 1997. She is the fourth of seven children, including her half-siblings Helen and Mark, and was born within minutes before her twin brother Ty. Livia remains among the few people by whom Ty doesn't mind being touched, as well as one of the few people who can effectively calm him down.

A young Livvy was with Helen, Ty, Jules, and presumably the rest of their siblings while their family visited the New York Institute in 2007. According to Jules, she and Ty were eating wax, much to Helen's frustration.

Dark War
In December of 2007, the Los Angeles Institute was attacked by Sebastian Morgenstern and his Endarkened army. Along with her siblings (with the exception of Mark and Helen, the latter of whom was in Alicante at the time of the attack), Livia managed to escape through a Portal, which was opened by the Clave upon Jules' emergency request.

Once there, Livia was among the children who were interrogated with the Mortal Sword, after learning that their father was among the Clave members who were Turned into Dark Shadowhunters by the Infernal Cup. Eventually, they also learned that their brother Mark had been forced to join the Wild Hunt.

The next time they saw their father was during the battle in Alicante, during which the children were sent to hide in the Accords Hall. There, Andrew quickly found his children and immediately began to approach them menacingly. Jules saw that his father was truly gone after being Turned, and ultimately killed him before he could hurt Ty or his other siblings. When Ty threw a fit afterward, Livia tried to calm him down, knowing that Jules had no choice but to do what he did.

Eventually, the children returned to Los Angeles with their uncle, Arthur, who took over as head of the Los Angeles Institute.

Personality
Livia is in fact as peculiar as her brother Ty, though in a very different way; while Ty is immediately seen as the oddity in their family, she is, at first glance, seen as normal and ordinary.

Livvy is also mathematically-minded. She is fascinated by fractal patterns. She would often help her siblings when they struggle with their math. She and Ty picked up the hobby of studying computers—where Ty liked analyzing and organizing the patterns, she was more involved with the mathematical aspect the programming and coding. Sometimes even her tutor Diana wishes she could go to college and take a higher level math course.

Affected by their experience in the Dark War, Livvy believes it is her job to protect her whole family, thinking that they are all a bit on the hapless dreamer and starry-eyed artist side. She is incredibly protective of her family, especially Ty. Livvy is also very practical.

Physical description
Livia, like her other siblings, has the Blackthorn brown hair and blue-green eyes. Livvy was born with gray eyes like her twin, Tiberius, though hers had changed to blue-green since. Both also have long lashes and cupid's bow lips.

Skills and abilities

 * Nephilim physiology: Being Nephilim, Livia possesses a variety of enhanced physical and mental abilities granted to her by the blood of Raziel in her veins and also by the angelic Marks of the Gray Book. She also has the power to perform tasks unique to their species, such as the ability to use and call on the power of angels for their seraph blade. This includes enhanced strength, agility, stamina, and coordination, which only improves over time and practice.
 * Runic magic: Due to the angel blood in their veins, all Shadowhunters are able to apply runes on their skin without any real danger. These Marks, in turn, give varied effects that serve to benefit the wearer.
 * Swordsmanship: Livia is a skilled fencer and sword fighter. She favours the saber.

Possessions

 * Stele: a typical Shadowhunter paraphernalia, used for drawing Marks on their skin.
 * Poison darts: Livia's favored weapons.
 * Saber: Livia's favourite weapon.