Karl Fei-Ong

Karl Fei-Ong was one of Diva's chevaliers and a member of Cinq Flèches, as well as the chairman of Lycèe De Cinq Flèches, a renowned girls' high-school in Vietnam.

Background
In 1917, Amshel Goldsmith chooses Karl Fei-Ong to use as a test subject for their new Delta project. He and Solomon Goldsmith introduce Karl to Diva in Germany. When he meets her, he requests her to turn him into a chevalier.

Karl's body is heavily modified by Amshel's experiments, including having the arm Saya destroyed in Vietnam in 1972 replaced with a spiked arm. His traumatic past, Diva's inability to give him the love he sought, and forced conversion seems to have left Karl severely mentally unbalanced. However, Solomon, the only one who could calm Karl's mania, believed Karl's problems stemmed from his being lonely and not seeing that Solomon was always there and watching over him.

Human form
Karl has the appearance of a handsome, elegant young Vietnamese man who, according to the Light Novel, seems to be in his mid to late 20s. However, in reality, he is over a 100 years old.

He has long jet black hair which is lower back length, with side bangs falling past his chin. He wears part of his hair in a bun tied back with a burgundy ribbon wrapped to hold it in place with .While the rest of his hair is flowing loose.He also has dark grey eyes which turn crimson red when enraged. Along with this traditional hairstyle, he is always wearing an ultramarine Vietnamese ao-gam. As his alter ego, Phantom, he abandons the traditional hairstyle and lets it flow loose. To disguise himself even further, he wears a mask for a short time until his identity is known to the member's of  Red Shield.

Chiropteran form
Just like other chevaliers, Karl possesses a chiropteran form. In this state, his skin is a dark blue and his usually flowing black hair changes into grayish tendrils that protrude from his head. He also has many rows of sharp teeth and has an unusual jaw as a line of flesh connects to the bottom and top on each side. As with other chiropterans, his eyes glow red, though unlike James and Nathan he can fly in this form.

Attire
He wears traditional clothing of his native Vietnam including a long ultramarine Ao Gam tunic with burgundy lining and burgundy clasps to hold the robe together and charcoal pants with black dress shoes. Furthermore, with this outfit he wears dark vermilion almost black gloves on both hands.He has the ability to change and alter his left arm into a weapon when he removes his glove.

When disguised as the Phantom, he wears a traditional black tuxedo with a tattered black cloak and a vermilion mask detailed with bat wings on the sides of the frames. The mask is designed to cover his right eye and match with this outfit.

Season 1
Karl Fei-Ong is the chairman of an all-girls school in his native Vietnam, where he is respected by both teachers and students. The girls themselves do not seem to fear him - they are polite and he is polite in return. Disguised as his alter ego "The Phantom", Karl kidnaps girls that look like Saya in his desire to see her again to finish their fight; before the girls went missing they were all given a blue rose. It's not clear whether he based "The Phantom" on the legend or whether the legend is based on Karl himself.

After finding Saya again, Karl becomes completely obsessed with killing her. He considers Saya his hated enemy, his beloved soul mate, and his only reason for living. He keeps watch on her in the school and gives her the legendary blue rose.

He follows Saya on the school trip where he corners her as 'the Phantom' in an alley. A clash with him results in him finding that Saya has no memory of her past as well as the revelation to Saya that he is the Chairman of the school.

He again confronts Saya during the ball where the Red Shield infiltrates to get to Diva's container. Saya's continuous failing at recognizing him or turning into her berserk form, which he admires, leaves him dissatisfied and he departs for his mansion.

During the Red Shield's investigation in the Vietnamese jungle, they discover a secret farming facility owned by Cinq Flèches under the management of both Karl and Solomon. Karl leads an attack on the group, using the Delta-67 experiments, (little children) which causes several casualties. Saya later fights Karl, which results in Karl losing his leg in the process and being forced to retreat.

Season 2
Karl finally gets his longed attention from Diva when she requested him to bring her "that boy". Karl (dressed as The Phantom) brings Diva to Red Shield's HQ without Amshel's authorization and begins killing all of the Red Shield operatives. He encounters Saya, but Hagi distracted him long enough for Saya to escape. Karl escapes the ship along with Diva and manages to wound Joel with his spikes, which would cause him to become permanently paralyzed from the waist down.

Season 3
While in London, he steals the Corpse Corps from Amshel after being outraged when James was given the orders to kill Saya instead of him and went after her while she was at Glay's home. He planned to die together with her by drinking all of her blood. Solomon, who'd come after him at Amshel's request, cuts off Karl's arm, freeing Saya's sword arm. Realizing she has too much to live for, Saya stabs him by impaling her own body. With her sword coated in her blood, Karl crystallizes and is destroyed. Solomon mourns his death and tries to explain Karl's actions.

Manga
In the manga adaption, Karl's appearance and mannerisms are completely changed. He's more childlike and is stated to look several years younger than Riku, who is fourteen. Karl is the only chevalier besides Amshel that Diva cares for. After losing his arm during the fight in Vietnam with Saya, he is forbidden from seeing Diva again and loses his status as a chevalier, becoming a living experimental subject for the next generation of chiropterans. He is then renamed "Charles" by Amshel. His renewed form is later killed by Saya.

Personality
Karl is usually calm, mature and very controlled as the chairman. He is also very polite as shown when someone says hi he says hello in return however he suffers from multiple personality disorder having two split personae himself and the phantom.

His second personality - the Phantom is violent, sadistic, obsessive and very cruel. He often speaks in very eccentric ways such as calling a fight a dance.

His maniac behavior stems from being used as a guinea pig in the Delta Project, repeatedly having his limbs removed and replaced. He is also very sneaky shown in eavesdropping on Saya's conversation with Haji and sneaking in to diva's container despite seeing the cameras.

Diva
Like his brothers, Karl is very fond of Diva. However, their bond is described to be dangerous and unhealthy for Diva, possibly due to the fact that both are quite reckless when left alone. Yet, after some time, when Karl becomes more mentally unstable and obsessed with killing Saya, Diva begins to reject him. This causes him to act out, resulting in his own demise.

Saya
Karl considered Saya as an enemy and a soul-mate that was his "only reason for living". Saya was the very cause for Karl's arm being destroyed in Vietnam and his uncontrollable mania, which resulted in Diva rejecting him. Because of this, Saya was the first person he could turn to for comfort, believing her to the only person who could love him. He attempted a murder-suicide on her in their final battle, hoping to take them both to a world where they belong together, but fails.

Solomon
Karl and Solomon are the closest out of all of their brothers in the group, whereas Solomon harbors great sympathy and envy for Karl. This sympathy, however, seems to be the result of Solomon's own guilt - not only was he the one who tricked Karl into becoming a chevalier, he also aided in his death. With Karl being the one most distant from the other Chevaliers in the group, Solomon phones him with updates from time to time when the others refuse to keep in contact with him.

Amshel
In complete contrast to Solomon, Karl fears Amshel, possibly because he organized the many operations performed on him. Amshel intentionally antagonizes Karl, noticeably by insisting James kill Saya despite the fact Karl volunteered first. Later it is revealed that he does this to deliberately provoke Karl into chasing after her, giving him an excuse to kill him.

James
Like Amshel, James appears to have nothing but disdain for Karl, characterizing him as careless or reckless, and seeing his death more as a convenience than a loss to them.

Nathan
Karl does not interact with Nathan. However, in the novel, Nathan playfully teases Karl when Diva ignores him, but Karl does not acknowledge him.

Special Abilities
Enhanced Strength: Like other chevaliers, Karl has enhanced strength.

Enhanced Speed: As a chevalier, he sports great speed. However he is outpaced by his other brothers.

Transformation: In his true form, his original power was to make a blade from his hands. After having his right arm replaced by Amshel with a spike arm, he gained the Schiff's ability to crystallize his blood and fire it from his arm. He is also capable of flying as he possesses a pair of wing each located underneath his arms.

Healing: Like all Chiropterans, he has great healing abilities, recovering from stab and gunshot wounds within moments.

Extra Sensory Perception: Stated in the light novel, Chiropterans have the ability to sense other Chiropterans. Karl's ability with this is greater than James Ironside.

Weakness: His weaknesses, like all chevaliers, include Saya's blood and, if Amshel was telling the truth, decapitation and complete incineration of the body. It is unknown whether or not that he, like James, could contract the Thorn.

Trivia

 * The phantom's eyes are often depicted as being small pupils probably to add to the insanity that he has.
 * Karl seems to have an interest in traditional clothing as he is never seen in a suit or modern clothes and is almost always wearing an ao dai which was usually worn in the 18th century but is considered classic clothing in the 21 century.