Ollerus

Ollerus (オッレルス) is a mysterious fellow that once had the chance to become a Majin, but failed. Still, he is stated as one of the strongest characters in the series, and is currently being pursued by various magical organizations seeking his power and knowledge, but he has managed to elude all of them with ease.

Etymology
Ollerus is the romanized name of a legendary Norse God named Ullr. Kanzaki Kaori explicitly refers to Ollerus' namesake in the Norse Mythology SS, confirming the author's intentions.

Background
Not much is known about Ollerus' backstory. He has a history with the Saint Silvia, who was travelling the world to hone her Bonne Damme skills; how they met and the circumstances behind it are unclear, but it appears they've known each other for awhile. She's quite cruel to him on the surface and scolds him for being an "idiot to the core", but still cares for him deep down and feels an urge to protect him, and it is heavily implied she is in love with him. Silvia says Ollerus is a "damn dust-covered ruined noble", that he keeps getting wrapped up into all sorts of troubles ever since he failed to become a Majin, and that he sometimes cries late into the night when remembering the missed chance. There seems to be great antagonism between Ollerus and One-Eyed Othinus, the one who stole the title of Majin from him.

Personality
Ollerus is kind-hearted and sentimental person, to the point where he squandered the once in about 10,000 year chance to become a Majin in order to save a cat. He also destroyed a human trafficking organization and saved one-hundred children, when he did not need to, and did it knowing full well he would have to face Silvia's wrath over his overtly casual attitude. When one of the children he saved says she wants to repay him, Ollerus dismissed it by saying he didn't expect anyhing in return — a similar ideal Kamijou Touma holds. He also says that chaining up the human traffickers was meaningless because it was no different that what they did.

Thor points out a negative aspect of his methods, saying that Ollerus loses sight of his surroundings when he starts fighting, and does this with out concern for everything other then what he is trying to protect.

However, when the need arises, he shows a very serious attitude.

Appearance
Ollerus is a slim, short-haired blond man with green eyes, who wears a modest aquamarine thin shirt accompanied by a camel-coloured lambskin vest.

Toaru Majutsu no Index Light Novel Volume SS2

 * Main article:Toaru Majutsu no Index Light Novel Volume SS2

Ollerus first appears in Volume SS2, when he returns from the city of Milan in Italy. There, he destroyed a child trafficking organization and saved about one-hundred children. Since he had no idea what to do with them, he brings them to his and Silvia's apartment until they can find homes. There, Silvia berates him for making promises he can't keep and straddles him to the doghouse in their apartment's yard with rope, applying painful pressure to his crotch. Despite that, Silvia takes the children in. After dealing with that trouble, Silvia goes back to Ollerus, where they discuss that some of the one-hundred children were marked and shared certain characteristics — that of Gemstones. Ollerus disappears later that day.

We later see him infiltrating Academy City in order to put across a point to Academy City's Board of Directors and Aleister Crowley that if they misuse the Gemstones they took in and use them as lab rats in experiments, he will personally step in to stop them. Ollerus is confronted by nine of the ten Misaka Sisters remaining in the city, and he manages to defeat them all effortlessly. Then, on one of his patrols, the 7th Level 5 and greatest Gemstone Sogiita Gunha barges in on the scene and confronts Ollerus. Gunha, after seeing what Ollerus did to the Sisters, deems him a threat and attacks. Ollerus then uses the defensive spell called Hliðskjálf in an offensive way, which floors Gunha and knocks him down to the ground. Gunha, however, proceeds to get up without major injuries, and valiantly charges at Ollerus once again, only for the same result to occur. Ollerus says that Gunha doesn't understand his true powers, and that if he did, then he could defeat him. Gunha once again gets up and charges, though the battle cuts off there.

We later learn that Ollerus was victorious and Gunha is beaten into the ground. The difference between Gunha and Ollerus' powers was so large that though Gunha took Ollerus as a serious opponent and went all out, Ollerus was only toying with Gunha. Olerus returns to the apartment, where he is greeted by Silvia and some of the children he saved.

World War III Arc

 * Main article: World War III

Ollerus, having observed the Third World War from the sidelines, appeared at the end of Volume 22 with Silvia to rescue a dying Fiamma of the Right from the snow after his defeat at the hands of Aleister Crowley. Ollerus shows interest in Aleister's Age of Horus and says he can hide Fiamma if he tells him what he knows. Fiamma, asking who they are, is answered by Ollerus who introduces himself as the pathetic magician who had the position of Majin stolen from him by One-Eyed Othinus.

Baggage City Arc

 * Main article: Baggage City Arc

Ollerus makes an appearance by confronting his nemesis, One-Eyed Othinus. The Majin and leader of GREMLIN, having just severed Kamijou Touma's right hand and crushed the Invisible Thing that came out as a result, only sneers at the sight of "The Failure". Ollerus declares he's not here to fight her, and suggests Othinus leaves with the unconscious Marian Slingeneyer as he has business with the Imagine Breaker. Both of them spar and discuss the principles of purity of Magic Gods amid sneers, until Ollerus reveals that he is not alone and has Fiamma of the Right on his side — his Holy Right empowered by the fact Touma's arm had been severed by her, enabling his world-saving powers to activate. Othinus seemingly agrees with Ollerus' previous suggestion, but on a whim decides to kill them. The battle ends in a draw. With Othinus gone, He and Fiamma assist Touma and watch as his crushed arm is restored. The three, under Touma's insistance, begin to use their talents to analyse Marian Slingeneyer's methods so they can restore her victims to normal, including Cendrillon.

Ollerus later changes Cendrillon back to normal, somehow giving her the ability to reconstruct her body.

Ichihanaran Festival Arc

 * Main article: Ichihanaran Festival Arc

It is unknown how, but it can be presumed that Ollerus was the one who sent Touma back to Academy City, while he was unconscious. He, Fiamma of the Right, Silvia, Brunhild Eiktobel, and Leivinia Birdway, gather in Academy City to oppose Othinus and GREMLIN, who plans to capture Fräulein Kreutune, despite the fact that they could've intercepted them outside of Academy City, though chose to have the battlefield in Academy City in order to interfere with GREMLIN's teamwork, as Thor noted.

Ollerus later appears before Kamijou Touma after he was tasked by Fukiyose Seiri to buy some food for them. He notes on how it took so long for Touma to sense him, noting that he lost a bet with Fiamma of the Right, and says that he wants to talk about the Imagine Breaker to him, but Touma ignores him much to his surprise. Ollerus later gets the opportunity to talk to Touma after he ran his errands. Here, Ollerus tells Touma of what a Majin is, GREMLIN and Othinus' goals, his and his Imagine Breaker's role in it, as well as his opinion regarding the nature of the Imagine Breaker.

It can be assumed that Ollerus later receives a report from Leivinia after her confrontation with Touma, detailing him on how GREMLIN has won him over.

Abilities
Ollerus wields the power of Nordic Throne (Odin's throne), related to Norse Mythology, and his power has been described as incomprehensible and inexplicable. He almost became a Majin or "Magic God" — one whose's magical powers has reached the level of divinity, and so can bend all natural laws — but didn't. It has been stated that he has used the knowledge from a lot of grimoires, though any possible ill effects he suffered is not mentioned. It was said by Silvia that he uses the theory of Hliðskjálf to purify his own life force so that it transforms into a special magical power. This just barely allows him to survive the process of taking in a grimoire's knowledge within him.

Ollerus has described himself as an impure example of a Majin, yet he can still wield that power. Unlike Othinus, who is a perfect and pure Magic God, Ollerus stopped his growth at the point where he should have become a Magic God. Because of that, his overall powers are weaker, but he doesn't have the 50/50 dilemma Othinus has to operate under.

Until now, he showed only one of his abilities:
 * Hliðskjálf (北欧王座 (フリズスキャルヴ) ), it is his power to change life energy and normal magical power into an unexplainable type of power. The power by its nature cannot be described, can't be explained, and can't be comprehended. Since the power cannot be comprehended, there is no possible defense to stop it according to Ollerus. The actual Hliðskjálf (which is the throne of Odin) doesn't have any offensive function, but by forcefully using Hliðskjálf as an offensive power makes it even more unexplainable. He uses Hliðskjálf due to the fact that his own mana is too special and can't be used with normal magical powers, even if he applied knowledge of various grimoires. In other words, he needs the unexplainable energy to be used up by Hliðskjálf to prevent a build-up of mana inside him and self-destructs.

Design evolution
Ollerus' design remains static throughout the series. Haimura designed him as an opposite to Sogiita Gunha's intensity. He was given the same color as Index, due to her connection of being near a Majin, and had the print on his pants similar to the Jeans Slasher, as she is also related to Norse mythology, somewhat.

Quotes

 * (Ollerus reacting to Silvia's cold indifference to the children): "That’s too cruel!! There’s no way I can do that, you heartless woman!! Are you someone’s animal-hating mother!? Reaching out a hand when someone is in need is the basic law of the world!!"
 * (To a child he saved in SS2): "I am glad you adore me, but I didn’t really do anything. Chaining those human traffickers up and making them do manual labor is no different than what they did. That isn’t what I want."
 * (To Sogiita Gunha in SS2): "No, I really have no guts. But I have my reasons. Unlike you, I have a reason to fight."
 * (To Sogiita Gunha in SS2):"The most fearsome thing in this world is to be defeated by an attack using an unexplainable power coming from an incomprehensible place while you have no way of thinking up a counter measure. The attack is vague and you cannot assign conditions to it and you don’t even know if there is a direction you can go to avoid it or if you could even avoid it after getting tens of thousands of kilometers away. You now know how horrible that is firsthand."
 * (To Fiamma in Volume 22): "I am a pathetic magician who once should have become a Magic God, but had that position stolen by One-Eyed Othinus."
 * (To Othinus in NT4): "No, I don’t think I can win. If I could, I would have killed you long ago. I will abstain from killing you as long as I have no means of doing so. That’s all there is to it."
 * (Regarding his power compared to Othinus): "I am an impure example that stopped at the point where I ‘should have’ become a Magic God. In other words, I lose to you in overall power, but I am freed from that 50/50 dilemma. After all, I am imperfect. Unlike your perfect balance, my odds of victory have a deviation."