Isabella Theism

Isabella Theism (イザベラ＝テイズム) is a necromancer and member of Necessarius, introduced in Toaru Majutsu no Index SS: Agnese's Magic Side Work Experience.

Etymology
is an Italian name, a Latinized form of the Hebrew name Elisheba (meaning "God is my abundance" or "God is my oath"), from which Elizabeth is also derived. is a term referring to belief in God or gods, derived from the Greek theos or theoi (meaning "god" or "gods").

Appearance
Isabella is a gaunt, silver-haired and brown-skinned woman, who dresses in tattered rags, clothing of the dead. She wore a necklace with a cracked heart and has a skull symbol on her head.

Personality
Isabella is described as eccentric for her choice to wear the clothes of the dead as her regular attire.

Background
At various points in the past, Necessarius has had Isabella create and place fake corpses to deliver a desired impact against certain enemies. She has worked together with Stiyl Magnus on several occasions before the Agnese Forces training in Barcelona, with Stiyl having seen her casually cut down magicians just as they had managed to escape the labyrinth of fear and doubts she had created and thought that they were finally safe again.

Toaru Majutsu no Index SS: Agnese's Magic Side Work Experience
During Agnese Sanctis, Lucia and Angelene's training for Necessarius, Isabella fought Stiyl in a mock battle in Barcelona, Spain, which the nuns were to forensically clean afterwards. In the simulated battle, Isabella was playing the role of a member of the magic cabal Armada who had been burying people alive to create a graveyard for the burial shrouds needed for her magic.

Later on, she and Stiyl watched as the nuns dealt with a curse-fearing priest, who had applied magical cleaning techniques in order to frame and dispose of a Haitian restaurant owner whose wife had apparently died from a curse, with Agnese dumping the remains of Isabella's fake corpse on the priest. With the girls having passed the test, Isabella noted that they were about to be very busy.

During the summoning incident, Isabella was present when the five magicians who had used the shared ceremonial ground within the past month were gathered and spoke to make them more compliant for interrogation. After the incident, Isabella talked with Agnese about the feelings that prompted Jack Prometeria's actions and their relation to her field.

While the nuns were in Frankfurt, Isabella mentioned information to Agnese concerning bike delivery workers in the city going missing, luring the nuns into carrying out a sting operation when they discovered Angelene had been doing a similar job part-time for snack funds. Later, when Angelene was being pursued by the demon from the Ceremony of Ba Moun and trapped in a restaurant, Agnese and Lucia captured Isabella, who was observing from a nearby rooftop, tied her up and had her tell them what she knew of the situation and how to stop the curse, under threat of catapulting her into the restaurant. Isabella managed to deal with the demon using two fake corpses modelled after its true target Frau Halveria, leading the demon to tear itself apart, before handing her a mop to clean up the remains.

Abilities
Isabella is a necromancer who is skilled in creating corpses for fear, confusion and deception. Using only pig and cow remains in her work, she can rearrange the bones and organs to match human anatomy, treat it with chemicals, and produce a high quality imitation of a dead human body. These fake corpses can be designed after an enemy or ally and left in a crucial location to deceive or inspire fear and confusion. While some others might produce higher quality imitations, she is unrivaled in terms of cost-performance. She can also control her corpses remotely.

Isabella is skilled at creating and exploiting the doubts and confusion resulting from her use of corpses, and has been described as the type of magician who can win a battle without actually fighting, though she is fully capable of fighting if necessary.

One form of necromancy which Isabella uses involves the living donning the stolen clothes of the dead (clothing being a symbol of position) in order to become one with them and draw on their power. The tattered rags which Isabella normally wears are such clothes. In the mock battle with Stiyl Magnus in Barcelona, Isabella made use of a long cloth, a spiritual item created by sewing together burial garbs, apparently obtained via grave-robbing, and based on a mixture of Voodoo and the Christian. It was capable of spiraling around Isabella, bending down like a spring and launching her over ten meters upwards onto a rooftop.

In the same mock battle, Isabella made use of Voodoo-based techniques in conjunction with a substitute corpse prepared for the training exercise. With the vocal command "Detach the Ti Bon Ange and place it within me" and breaking open a capsule of zombie powder (which she might have stored within ) hidden in the canine tooth, an entity (possibly a summoned soul or something which seemed to be one) was drawn into the body and moves it on its own, regardless of damage. When bisected, tentacles emerged from the lower half of the body, and when the upper half would have been burned away, a disembodied brain in a transparent shell and supported by many tentacles (resembling a jellyfish) burst out of the skull and leapt away in a final effort to escape.

The corpse was apparently infected with a Voodoo curse, meaning the nuns needed to be careful during cleanup and disposal. During the cleanup, some clumps of flesh started to tremble and move, with the possibility of coming together to form a. It was also noted that AEDs and epinephrine were off limits as trying to revive the corpse could cause the soulless doll to get up and start moving.