Aidan Kain

Aidan Kain (エイダン・カイン), real name Somnus, is the main protagonist of Highschool DXD: The Prime Evil. He is Rias Gremory's pawn and the host of one of the Prime Evils Al'Diabolos, or known more commonly as Diablo, through the red soulstone he injected into his forehead.

Appearance
Aidan is a tall, slim, well-muscled, and handsome man with black short hair and blue eyes that attracts a lot of girls to him, mostly the 3rd-year females. He wears the usual Kuoh Academy boys school uniform but with black dress shoes instead of the brown ones. His casual attire at home is consisting of a gray tank top, black short sweats, and brown sandals but his public appearance is more casual. It consisted of a gray shirt covered by a black buttoned shirt, gray khakis, and black dress shoes.

As the Dark Wanderer, Aidan wears a full-bodied cloak to conceal himself when he travels on Earth in disguise. His face is obscurely seen as only a part of his face is revealed with a small red shine on his forehead from the soulstone and red demonic eyes.

When transforming into Diablo, Aidan appears as a hulking brutish red demon beast with black spikes protruding from his back, arms, tail, and head. The red soulstone is shown sticking out of his forehead.

Personality
Unlike Issei, Aidan is regarded as quiet, cold, and strict but is kind and affectionate to others. He will willingly help those in need from trouble and has no problems getting into fights with the males that are jealous of him. While highly knowledgeable and respectable to his fellow classmates, except for the Perverted Trio and other jealous males, he often acts and speaks in a low voice. When he does speak though, he has a down-to-earth personality and focuses on reality and the present while trying not to worry too much of the future or the past. He stays focused with a calm mind in battle, even if it sometimes means he has to go to extreme measures to protect the people he cares for.

Initially, Aidan believed that because he is the host of Diablo itself, he should not be too close to anyone out of fear of hurting them with his power. He is also afraid that because of obtaining such power, he will eventually be consumed by it over time, no matter how much he trains to resist. At one time, he sought to seal himself away so as to not lose control to Diablo and set him loose upon the world. To that end, he detached himself of any emotion until that was restored by Rias, whom he soon fell in love with. He cares for the people around him yet will willingly put people in their place by using the power of Terror to ensure that they do not do something reckless or to reprimand them of their behavior. And unlike Issei who excites himself over the presence of a naked girl, Aidan is not embarrassed and does not mind if a girl(s) like Akeno or Rias sleeps with him or whether they want sex with him.

As Diablo, Aidan is incapable of feeling fear due to his mastery over terror. He is the most creative and farsighted of Rias' peerage and the strongest of her pieces. Calm, cunning, and patient, Aidan sees himself as an artist of terror. He knows that conquest comes when enemies turn their back on fear rather than face them. But Aidan does not acquire satisfaction from conquest itself as he rather feeds on the terror that precedes the conquest. To him, the fear of a victim has/is a greater reward than the pain they suffer when they are actually tortured. As his power increased, Aidan became darker and more terrifying with his words against his enemies, becoming more and more like Diablo.

History
Aidan’s parents were unknown, but he grew up under his adoptive uncle, Deckard Kain, a university religious studies professor who is aware of the supernatural much to the surprise of the ORC. He learned much from his uncle’s writings about the angels and demons, the Eternal Conflict, the Great War, and the Sin War. Along with his uncle, he is a member of the Horadrim, an ancient order of mages created to secretly guard the world from the incursion of the demons with Deckard being the last. While he did not have a hard time growing up, Aidan did not make a lot of friends and was often studying, sometimes looking into his adoptive uncle's scholarly works or working out and training.

Over much of his life, Aidan and Deckard would travel around the world, hunting supernatural artifacts and lore that would help them understand more about the supernatural. Often, they ran into trouble though, mostly from the demons of the Burning Hells that cropped up from time to time while other times were Stray Devils or Fallen Angels. Their travels led them from the papal tombs in Italy to the ancient temples of China, the Mayan ruins in South America to the primitive tribes of Africa, where they found ancient Horadric relics carried by actual members of the Horadrim. Their last stop would be in Kuoh Town, Japan, where Aidan was transferred in as a 2nd year student at Kuoh Academy, unaware that he gained the eye of the Academy's two most popular women.

Plot
Like Issei, Aidan was lured into a trap by Dohnaseek and nearly killed him had it not been for Aidan’s solo training. Aidan fully knew of Dohnaseek's intention and of his true nature and managed to destroy him before succumbing to his eventual wounds. As he laid dying, Aidan was reincarnated as a devil by Rias Gremory, beginning his life as a devil. However, in the reincarnation process, someone from the shadows intervened to prevent Aidan from being turned into a devil, using their magic to keep his true nature intact whilst resurrecting him.

He was then introduced to the rest of the Occult Research Club and it’s new members. Upon activating the Sacred Gear inside of him, Aidan was given a Sacred Gear completely unknown to everyone; Al’Diabolos Terror Claws. But unknown to Aidan, the Lord of Terror, Al'Diabolos, reached out to him from his soulstone and gave him this Sacred Gear so as to manipulate him for his freedom.

After Riser's victory in the Rating Game, Aidan knew that in order for him to beat Riser and save Rias, he needed more power. Thus, he convinced Grayfia to take him to the Gremory Family's treasure vault where, deep inside and under heavy guard, the red soulstone of Diablo, the Lord of Terror, was kept. In return for taking the soulstone and using its power to defeat Riser, Aidan will disappear and seal himself away to battle Diablo for eternity, alone and forgotten. Initially hesitant and resistant at first, Grayfia complied and watched as Aidan thrusted the soulstone directly into his forehead. Blood filled his vision as screams of terror and whispers of the damned echoed in his ears, the soul of the Lord of Terror entering through his body as the demon clawed his way up from the dark recesses of his soul. But against all odds, Aidan had done it. He had contained Diablo's essence.

After crashing the ceremony, Aidan slaughtered the guards and put fear into everyone before slowly beginning to reveal his new form while he tapped into his new powers. Temporarily taking partial form of Diablo, Aidan was easily able to defeat Riser to the point where the Phoenix became heavily wounded and psychologically scarred. Aidan would've ended Riser's life had it not been for Issei who intervened. Aidan almost struck a defeated Issei down but was halted as he struggled against Diablo's will to which he was barely able to succeed to contain him. But in the belief he had betrayed Rias, Aidan fled from the Underworld, knowing that truthfully, he had not contained Diablo at all. Thus, in an attempt to remain in hiding and find a way to seal himself and Diablo, Aidan took the moniker of The Dark Wanderer and traveled back to Earth, heading to the forgotten kingdom of Khanduras.

Arriving at Tristram Cathedral, Aidan descended down into the haunted building and attempted to bind himself to a prison chamber to battle Diablo for all eternity underground and away from the world, believing that he will be easily forgotten. His plan was thwarted by the timely arrival of the ORC and Sona Sitri’s peerage. Losing control to the Lord of Terror within, Diablo took control and used Aidan’s body to engage in battle.

Diablo first fought Rias single-handedly, the latter separated by her peerage. Despite their vast differences of power, they fought each other to a standstill as Diablo commented of Rias' rage, and wondered aloud if the Gremory heir feared of how her peerage saw her of what she truly was. Rias angrily responded that she feared nothing and continued fighting but was incapacitated shortly afterwards.

It was at this point that the rest of Rias' peerage, along with Sona's arrived, saving Rias and incapacitating the Lord of Terror. Akeno and Sona suggested capturing him, for if slain, Diablo would return in time. An enraged Rias however, declared that demons like Diablo could only be dealt with through blood, and slew the Lord of Terror with her Power of Destruction.

In his last words, Diablo mocked the peerage for its supposed unity and states the return of the Prime Evils. With Diablo defeated, the demon was resealed away inside the soulstone, but Aidan fell into a three week coma.

Waking up back at his home with Rias watching over him, Aidan fearfully and regretfully apologizes for his selfish actions, believing that he betrayed Rias by containing and unleashing Diablo that would threaten everything. But Rias forgave him, relieved that she got her favorite pawn back, while also proclaiming her love for him that he returned.

With the Four Great Satans placing seals on Aidan, he returned to the ORC a changed man, now finally understanding that despite being the host for Diablo, he has not lost his will yet. His uncle Deckard Kain then arrives, revealing to have learned what Aidan has become and acknowledging it, knowing that he has such strong friends who can help him overcome Diablo inside of him.

But for Aidan, he knew that this was only the beginning...

Powers & Abilities
Immense Nephalem Power: Because he was born nephalem, half angel and half demon, Aidan is gifted with an ancient power not seen since the Worldstone’s destruction. With it, he can eliminate enemies easily but the power is often out of control, at least because he was unaware he was nephalem. It is also what has given him such strength, speed, endurance, and stamina due to his blood.


 * Immense Stamina: Aidan possesses a great amount of stamina, being capable of maintaining his Balance Breaker for half a year.


 * Immense Endurance: Aidan has an extreme tolerance to pain, even after being heavily wounded in a heavily exhausted state.


 * Immense Strength: Aidan is powerful as the host of Diablo as it would take the combine might of the Three Factions to strike him down. While also training his body to become stronger physically, Aidan is at his most strongest in his form as Diablo.

Immense Demonic Power: With the power of Diablo coursing through him, Aidan is considered to the strongest person in existence, almost as powerful as one of the Four Great Satans. His power allowed him to achieve his Balance Breaker and, with proper training, tap into various powers. He has even managed to obtain the Power of Destruction and the Phoenix Fire, as it is revealed that Diablo was its progenitor. Even when hit by a strong attack or afflicted by a dangerous poison, Aidan’s demonic power keeps him alive and endure such pain.

Telepathy: Aidan can communicate via telepathy so as to express his thoughts and emotions without having to use his speech most of the time. He can also use his telepathic powers to hold someone in the air, push them back, or even choke them.

Magic Talent: Trained by his uncle, and to an extent Diablo in the art of magic, Aidan became talented to the point where he was able to wield the chaotic energies of the Lord of Terror.

Equipment

 * Al’Diabolos Terror Claws: the main weapon of Tathamet’s Relic that spawn arm blades on the knuckles, the claws are able to cut through anything, armor or otherwise, and can leave wounds that slowly fade to become scars, never to heal so as to implement a psychological fear into the victim.
 * Balance Breaker: Primal Terror Vengeance: Similar to Issei and Vali's Scale Mail, Aidan’s generates a full-bodied demonic-like armor that drastically increases the users power, abilities, speed, and defense. It also temporarily allows Aidan to use the power of his Sacred Gear without the 10-second interval. The main difference between Aidan’s and Issei's and Vali's is that Aidan's armor comprises of both nephalem and demonic visages, displaying his true nature. Once he assumes this form, his power is nearly equivalent to that of the Twin Heavenly Dragons.

Silentium: A large two-handed (yet sometimes wielded with one hand) sword crafted after Aidan achieved his Balance Breaker, it is a platinum-colored longsword with a wing ornament at the hilt and a decorated blade. It is able to perform a unique warp strike when thrown. It became Aidan's main weapon after he discarded his first blade, Dawnbreaker.

Relationships
Rias Gremory:

Akeno Himejima:

Asia Argento:

Deckard Kain:

Trivia

 * Aidan Kain's name derives off of two people: Prince Aidan of Khanduras and Deckard Cain, both from the Diablo franchise.
 * His appearance is based on Noctis Lucis Caelum from Final Fantasy XV.