Ability Body Crystal

Ability Body Crystal or Crystallized Esper Essence (能力体結晶) or simply Body Crystal (体晶) is a drug that is used to induce an esper to overload, allowing them to temporarily gain power if they are espers that can only activate their powers if they are overloaded.

It was originally created and overseen by Kihara Gensei as a means to achieve SYSTEM.

Appearance
The First Sample of the crystal originally looked like a small red crystalline prism.

In a later incarnation, it becomes a fine white powder. In the Toaru Kagaku no Railgun S anime however, it is depicted as a white chewable tablet.

Concept and Creation
According to Gensei in his presentation to other Academy City researchers, overloaded espers (espers who has lost control of their powers) form abnormal synapses within their cerebral cortex. A large variety of neurotransmitters and hormones are secreted in unusual quantities. This crystallized esper essence is the product of collecting, refining and purifying those secretions.

Theoretically, applying the crystallized esper essence to selected espers, one can achieve SYSTEM or level 6. Exposing the crystal to overloaded espers with the same ability, and to another esper who has the same ability and can achieve higher levels of power when exposed to certain factors (such as Haruue Erii ), one can cause an AIM Diffusion Field Resonance thereby causing the resonance to power-up the esper, allowing the achievement of a level 6. However, such a case would cause undesirable effects to the espers, and to the surroundings as a consequence of creating a Poltergeist is likely.

Mechanics
The original First Sample was red and crystalline, and required an entire laboratory on its own with biopods for it to properly expose an esper, specifically, Haruue Erii, with the right frequency using the crystal. Although, this can be assumed to be because Therestina wanted to use runaway espers to induce an AIM Diffusion Field Resonance with Erii, and that normal exposure or intake of the crystal results in an overloading of the esper in question.

Later, with the powdery version of the crystal, it only requires for an esper susceptible to it, like Takitsubo Rikou, to lick it for it to overload her. In the Toaru Kagaku no Railgun S anime, they are turned into tablets and must be ingested for it to be used.

Regardless, if one is exposed to the crystal, it would cause the esper's ability to overload, as with the case of the Child Errors experimented on by Gensei.

First Sample
With the intent of achieving SYSTEM, Kihara Gensei uses his own granddaughter, Therestina, as the first test subject for the crystal, known as the First Sample. It is unknown what results were drawn out of the experiment were, though it is safe to assume that the experiment encourage Gensei even further into perfecting the crystal. Therestina lived through the experiment, but it is also unknown what effects the experiment had on her; it is known that even though she was used in the experiment, she still continued to support her grandfather, even helping him in his research as an assistant. Before the events of episode 24 of the anime, Therestina has gained possession of the First Sample, the same crystal that was created from her.

Kihara's presentation to Academy City researchers
Some time later, Kihara Gensei gives a presentation on the crystal to the city's academic community. Here, he explains how it was made and how it can be used to achieve the goal of SYSTEM. He receives the suspicion of Heaven Canceller, one of Academy City's most influential doctors, who asks him if the crystal can truly achieve level 6, which Gensei assures him it would. Heaven Canceler also asks him how many victims have been sacrificed to create the crystal, which Gensei says that there were no victims in his tests.

Beginnings
Gensei had control over the Advanced Education Department, wanting to use the Child Errors there as experimental samples for his crystal.

The experiment was officially called the AIM Diffusion Field Control Experiment (AIM拡散力場制御実験) to the public. As with its name, it was supposedly an experiment to control the AIM diffusion fields of the esper. However, the experiment also had another name Experiment on the Analysis of the Laws of Induced Explosions on Runaway Espers (暴走能力の法則解析用誘爆実験) to lead away investigations regarding the true nature of the experiment with exposing them with the Crystallized Esper Essence. Here, the experiment's goal was to search for the trigger for overloading AIM diffusion fields in espers.

He hires one of the researchers, Kiyama Harumi, to prepare the children for him for the experiment as a teacher to them.

The experiment
The experiment goes as planned, however the Child Errors goes into an indefinite comatose state after having their abilities overloaded by the crystal, Gensei forces everyone in the research team to gather data instead and them to keep quiet of what transpired in the department. Harumi is appalled by the experiment and quits shortly after, the comatose children are then sent to various medical institutions for treatment, but are unable to recover from their comatose state.

Aftermath
From then on Gensei disappeared, continually trying to perfect they crystal and make adjustments on it, though, Therestina refers to his action as useless.

Somehow a fine powder version of the crystal became available in the dark side of Academy City, though, its creation is credited to Kihara Gensei and Therestina Kihara Lifeline in the experiments that created the Crystallized Esper Essence.

Poltergeist Arc
The Crystallized Esper Essence is not mentioned until episode 22 of the Toaru Kagaku no Railgun anime; here, Kiyama Harumi reveals to Misaka Mikoto, that the experiment on the Child Errors on analysing the overloading of esper abilities, was a ruse as to discretely test the crystal on the children. Harumi also states that she is looking for the First Sample, a vital part in helping her students recover from their comatosed state, without them causing another Poltergeist Incident.

When Therestina's true identity is discovered by branch 177 of Judgment, Misaka Mikoto confronts Therestina herself. After being defeated by Therestina, she reveals to Mikoto on continuing his grandfather's work on achieving level 6, and mockingly give thanks to her for finding the comatosed children for her.

In the final episode, it is revealed that Therestina has the First Sample of the crystal in her hands, and planned to use Haruue Erii, along with the comatosed children of Kiyama Harumi, to cause an AIM Diffusion Field Resonance, allowing Haruue Erii's power to be boosted by the crystal, and finally achieving level 6. Her plan is stopped by Mikoto, Uiharu Kazari, Shirai Kuroko and Saten Ruiko, as the effects of her experiment would destroy Academy City. After being defeated, Kiyama Harumi uses the First Sample to finally wake her students.

Sisters Arc
During ITEM's take down attempt on Misaka Mikoto, Mugino Shizuri tasks Takitsubo Rikou to find her using her AIM Stalker, and has her use the Body Crystal. With her power activated, Mikoto is bombarded by Mugino's Meltdowner beam with terrific accuracy thanks to Rikou. Mikoto was only spared by the onslaught after Mugino realizes that she is dealing with Mikoto and would rather defeat her on her own.

Academy City Invasion Arc
During Yomikawa Aiho and Accelerator's talk, the narration references the experiment on the analysis of the laws of induced explosions on runaway espers as one of the many experiments that are conducted in the city to Child Errors.

Battle Royale Arc
Rikou using the Body Crystal against ITEM's enemies and being forced to by Mugino, forces Shiage's hand against Mugino, as Rikou's body continues to deteriorate every time she uses the crystal.

Here, Kakine Teitoku references the experiment on the analysis of the laws of induced explosions on runaway espers.

Trivia

 * 40% of the medical papers about Body Crystal came from labs funded by Sukunabikona Pharmaceutical.