Tecpatl

Tecpatl (テクパトル) is a minor character in Toaru Majutsu no Index. He was in charge of battle operations for the Return of the Winged One and acted as the cabal's leader after its previous leaders were overthrown.

Etymology
The is a flint or obsidian knife, used for human sacrifices and a symbol of Aztec Mythology.

Appearance
Tecpatl is described as a brown-skinned man somewhere between 25 to 30 years old.

Toaru Kagaku no Railgun SS: Liberal Arts City
Being in charge of battle operations, Tecpatl was involved in the Return of the Winged One's attack on the Liberal Arts City. According to his own words later, he supported the war with the 'World Police' in the belief that once the battle was over they would be able to live peacefully, though ultimately nothing changed for them.

After the war ended and the cabal's previous leaders were eliminated, Tecpatl took control of the organization. At some point, he conceived and implemented a plans to arm the common soldiers of the cabal with original grimoires for use as weapons. He also devised means to protect the wielder from the grimoire's knowledge.

Following the Liberal Arts City incident, Tecpatl took the punished Tochtli, rendered unable to think, in order to use her bones as raw material for his grimoire's projectiles.

DRAGON Arc
At some point prior to the events in the evening on October 17th, Tecpatl, accompanied by Tochtli, infiltrated Shiokishi's bodyguard, disguising himself as Minobe, leader of one of the two groups. He had intended to wait for chance to take Shiokishi's place in order to use his authority as a member of the Academy City Board of Directors to access GROUP's personal information and hunt Etzali down. However, Shiokishi's attempt to eliminate GROUP for seeking DRAGON and their subsequent attack on his fortress presented another opportunity.

When Etzali infiltrated the shelter disguised as Oyafune Monaka, Tecpatl killed the other members of Minobe's bodyguard group before coming in with Tochtli when Shiokishi called for Minobe after Etzali had revealed himself and broken his Powered Suit apart. After stabbing Shiokishi with an obsidian knife, Tecpatl and Tochtli removed their disguises, revealing themselves to Etzali with Tecpatl declaring his previous plan and that he would take Etzali's head back to the organization.

While Etzali was wondering why the two were together and about using his spear on his former comrades, Tecpatl asked if he intended to face him with his puny spear and took a bookbag from Tochtli containing his own grimoire original. As Etzali recognized it, Tecpatl remarked that it shouldn't be unthinkable for him to wield one, seeing as he was the one who conceived and implemented the plan for even common soldiers to be armed with them. He then challenged Etzali to bring out his own grimoire, stating that they knew Xochitl was alive so it would have to be in his possession.

When Etzali spoke out loud about records of the Moon Rabbit being present, Tecpatl confirmed that his grimoire was indeed derived from the legend of a rabbit being thrown at the moon during the creation of the Fifth Sun, and demonstrated its application by firing a shot which broke through the shelter's walls and struck Shiokishi's forces fighting outside. As he warned Etzali not to dodge or others would die, Etzali noticed Tochtli's condition. Tecpatl then revealed how the Tochtli's bones were being used as the raw materials for his projectile attacks, saying with a laugh how not even half of her bones remained and how the grimoire's process of replacing bones with obsidian was apparently excruciating, though it was fine with him as long as the 'rabbit bones' were replaced. As the enraged Etzali unleashed his own grimoire, Tecpatl staked the leadership of the Aztecs in a duel to the death between the two and their grimoires.

Tecpatl and Etzali subsequently fought using their respective grimoires, with Etzali suffering due to the flow of knowledge into his mind, while Tecpatl didn't due to the measures he had taken to prevent it. Eventually, several of Tecpatl's shots got past the grimoire's defenses and struck Etzali, who was knocked him down and only escaped being torn apart due to the grimoire's protection. With Etzali left unable to stand, Tecpatl approached him, stating the gap in their experience and Etzali's inferior protection against the grimoire's knowledge compared to his own precautions. He then spoke of the Return of the Winged One's current situation before shooting to kill.

However the last shot from his grimoire turned back and fatally wounded him. Tecpatl then saw how Etzali had drawn words from the grimoire on the floor in his own blood, copying the contents and effectively passing the knowledge on while Tecpatl was launching his attack, and was reminded of how grimoires had a trait of helping those who would spread their knowledge the most, even turning against their own wielders if necessary. Tecpatl fell to his knees and then weakly collapsed, with Etzali accepting his grimoire, intending to save Tochtli.

Abilities
Being the person in charge of battle operations and military planning for the Return of the Winged One,   it was hinted that Tecpatl had a great level of knowledge on the magic practices of his magic cabal, though during his short appearance, he only made use of the appearance-borrowing charm common to the cabal's members (disguising himself as Minobe), an obsidian knife, and his original grimoire.

Having devised and implemented the plan to arm the members of the cabal with grimoire, he had also developed methods to protect the wielder from their poison, preventing the harmful knowledge from flowing in reverse during use and from coming into contact with their mind. It was also hinted that he may have developed some of the other methods of using the grimoires, such as the one used on Xochitl where her flesh was ground down and used as the base material for an original grimoire, fusing with the book in order to use it more freely. Though experienced in the usage of grimoires, Tecpatl didn't account for the tendency of grimoires to side with those who would spread their knowledge the most, which, coupled with his preventative measures to shield himself from that knowledge, led to the situation where his own grimoire killed him.

The original grimoire which Tecpatl wielded was an Aztec Calendar Stone derivative known as the Moon Rabbit (月 の ウサギ). It consists several stone tablets a few millimeters thick with Aztec writing densely carved onto them and held in a rectangular object resembling a student's bookbag, it is based on the story of the 's creation, in which the moon that was created at the time was equally bright and a rabbit was throw at it to weaken its glow. Using this legend, the grimoire can fire 'rabbit bones' as powerful projectiles for long distance bombardment, capable of smashing through the walls of a nuclear shelter. Human bones can be used as raw material for the 'rabbit bones' and the grimoire can use a recorded method to replace the taken bones with obsidian, a process which is apparently excruciatingly painful. When Tecpatl used the grimoire's spell, the shots were fired from his hand with a flash of light. Tecpatl claimed that it was originally a strike which could reach other astral bodies, putting the apparently reduced power down to the 'rabbit bones' he was using being inferior.

Quotes

 * (Towards Etzali while unveiling his Calendar Stone) “Oi Oi. Is using something that puny really alright? … I thought you would have definitely used ‘something like this’”.
 * (Towards Etzali) “By now you should know the fact that Xochitl had been ‘remodeled’ and had a ‘grimoire original’ inserted into her. In this situation where even the common soldier is armed with grimoires, for me who is the person that thought up this plan and implemented it, having a grimoire shouldn’t be something unthinkable”
 * (Towards Etzali after he unleashes his grimoire) “Now this is a battle between us. Let us exhaust our wisdom and fight for the position of the Aztec’s helmsman”