Arachne is portrayed as a calm and intelligent individual. She rarely, if ever, shows any form of distress other than mild irritation; she showed no irritation when Mosquito told her that BREW was damaged in the explosion and left useless, and even used it as an advantage to trick Shibusen into thinking they still had BREW intact by withholding the true information. Likely due to her abilities, Arachne is not above taking advantage of someone's weaknesses and using it influence them into joining her. She has done this using the Moral Manipulation Machine on Kim and Jackie and later on using her powers to influence Soul Eater Evans.
Arachne also seems to greatly enjoy champagne--the finest vintage. In almost all of her scenes, she is seen drinking one. When she had emerged after 800 years and met with Mosquito, the first thing she asked for was champagne. In the anime, she preferred to drink wine moments after being nearly strangled to death by Asura.
She carries herself in an aristocratic manner, as if she were from a noble stock. This is further supported by the fact that she prefers only the finest champagne. She is almost never seen standing up. Immediately after awakening, she was quickly seen atop a golem watching over the ongoing battle. When she wished to retreat, instead of simply walking away, she was carried off by Giriko. She was welcomed by her butler while walking on a red carpet and is driven by him in a luxurious limousine.
Like her sister, Medusa, Arachne also seems to express particular interest in "madness", eventually becoming madness itself within the Manga. While in the Anime, Arachne is instead allied with Asura but still plans to use madness created by Asura for her own goals.
Arachne has an extremely pale and flawless complexion, making it appear like she’s almost constructed entirely out of porcelain. She has a thin figure and very large breasts. Her facial features comprise of long dark black hair, worn in an upwards manner with two long strands that frame either side of her face, and eyes that have both completely grey irises and pupils, each containing a black spider web pattern.
Her typical clothing consists simply of a long black sleeveless dress; however, this dress is incredibly long, in that it completely conceals her feet, while ending in eight small trailing pieces of fabric. A narrow black band encircles her neck featuring a small spider emblem, that lies at its front, and eight extensions that protrude outwards upon the back, with four emerging from either side. Spider web netting branches the gap between the band and the dress, extending downwards from the aforementioned spider emblem. Two large "sleeves", separated entirely from the dress, are worn on her arms, ending just after her elbows. Each of these "sleeves" also display four protrusions, appearing at the ends of the significant amount of overhanging fabric. She also wears two spider earrings that hang downwards from her ears.
Arachne often carries a rather large black folding fan, that is garnished with a spider web pattern.
Arachne is known as the mother of all Demon Weapons. Following instructions found within the Book of Eibon, Arachne created a Demon Weapon by combining the shape-shifting powers of a witch, a normal human, and an inanimate weapon. This was, of course, done after killing the witch and the human, first. After this, she is hunted down by not only her fellow Witches, but soon Shinigami himself.
During her battle with Shinigami, Medusa, her own sister, betrayed Arachne and left her to perish. She ultimately broke her soul down to small spiders which, 800 years later, recollected and formed back into Arachne. In the period between these two events, these numerous spiders spread out throughout the entire world, gathering information in preparation for Arachne's return.
Unlike Medusa, Archne's magic is more focused on manipulating the enemy from afar, rather than for direct combat.
However Arachne is not without means of defending herself when confronted with a physical assault, as shown when she easily blocked an enraged Crona’s blade with her fan and then proceeding to parry it with a hard slap to the face.
- Thread : Arachne can create threads that leaves a person immobilized for an unknown amount of time - possible depending on how strong the subject is. In her disembodied form, it appears that she is able to produce massive quantities of these threads and launch them at her opponent. However, it is not seen whether they have the same effect as Maka is protected by her Black Blood dress.
- Mind Control : This type of magic allows her to pull a person inside themselves and control them by making them face their worst fears; should someone outside distract the targeted person, however, the spell will be broken. After leaving her body, the power of this spell increases to a level where it is able to completely incapacitate Medusa in less than a second.
- Despite being one of the Gorgon sisters within the series, she does not share the same name as one of the actual Gorgon Sisters of Greek mythology, rather she shares her name with a woman who was turned into a spider by the goddess of wisdom Athena, who also was the one who turned Medusa into her hideous form.
- Although Arachne's soul was shown to have what resembled spider legs protuding from the sides, when it was eaten by Soul it looked like a plain soul.
- When Black☆Star fought Mifune, Mosquito commented on how Arachne's sister was the one the created the Demon Weapon that was from Tsubaki's clan, possibly hinting at the third Gorgon Sister, Shaula
- Commenting on the way Arachne had 'died', like Giriko (who had not died but rather got a new body), Giriko presumes that Arachne is, in fact, alive, using trickery to avoid permanent death like Medusa constantly does