Eudial was the first member of the Witches 5 to appear in the Sailor Moon S season and Infinity arc. She showed tremendous expertise in computer programming and inventing weapons. Her powers were fire-based.
In the manga, Eudial taught the Mugen Gakuen philosophy class on etiquette in her guise as Yuko Arimura. She accompanied her students to a school camp on Mount M, and coincidentally was there as the Inner Senshi were staying nearby, visiting Rei at her own training camp.
During the night, Eudial led her students in a special ritual which was intended to sacrifice their souls to her master, Pharaoh 90. Sailor Mars and Sailor Jupiter discovered her, however, and interrupted the ritual. When Eudial was hit by Sailor Mars' Mars Snake Fire attack, she transformed into her gorgon-like Daimon form, and was killed by Sailor Moon.
Eudial was briefly revived again by Kaolinite in Act 31 with the other Witches 5, and attacked Sailor Mars. She and the others were killed again by Sailor Pluto and Sailor Neptune.
She was ranked at Level 78 and known as the warrior of the flame. Although never used, her death attack according to the Materials Collection was Fire Buster.
In the anime, Eudial's mission, given to her over the phone by Professor Tomoe, was to locate Tokyo civilians with Pure Hearts. Eudial created a program on her computer to observe the lives of everyone in Tokyo and select the most likely Pure-Hearted candidate. To extract these Pure Hearts, Eudial constructed the so-called Capture Gun that would shoot a projectile of energy and force the Heart Crystal out of the target.
After her computer selected her target, Eudial would pack a Daimon into her car (a white station wagon with the Death Busters symbol on the side) and drive out of the laboratory. Eudial's car would emerge from a secret entrance (in increasingly sillier areas of Tokyo), and she would drive off extremely erratically. Eudial had unfortunate luck in that her targets were nearly always acquaintances of the Sailor Senshi, and she was usually prevented from stealing the Heart Crystal by them. At that point Eudial would panic, call out the Daimon from her car, then leave the scene.
Eudial was present for nine episodes, the longest run of the Witches 5, and arguably made the greatest contributions for the Death Busters. While she was never able to actually steal any Heart Crystals, she did manage to locate two of the three owners of the Talismans as well as discover the civilian identities of Sailor Moon,Sailor Venus, Sailor Uranus, and Sailor Neptune. Also, besides inventing the Gun to extract Heart Crystals, she invented two flamethrowers, the Fire Buster and the Fire Buster II (which was much more powerful and had special features such as the ability to shoot glue).
After hearing of Professor Tomoe's dissatisfaction with her repeated failures and overhearing dangerous gossip about her from her coworker Mimete, Eudial rewrote her program for finding Pure Hearts to find the owners of two of the Talismans. To her surprise, the owners turned out to be Haruka and Michiru (it was unclear if the program would have showed Setsuna's picture as well, since the program only searched for two people), her main competition in the search for the Talismans. Since she knew their true identities, she left a phone message for them, telling them that she had located the Talisman owners and that if Haruka and Michiru wanted one last battle over them, they should come to the (currently under construction) Marine Cathedral.
They took the bait and arrived at the Cathedral, only to find that Eudial had booby-trapped it. After weakening the pair to exhaustion, she shot Sailor Neptune (who was attempting to protect Sailor Uranus) and then informed Uranus that she, too, had a Talisman. At that point the other Senshi showed up, distracting Eudial and knocking her down to another floor. Uranus, whose mission was to locate the Talisman all along, shot herself to release it. The Senshi thought that Uranus and Neptune were dead, but Sailor Mars was able to hear a faint pulse, bringing the theory that the Talisman keeper would have to be sacrificed into question.
Eudial suddenly returned at this point, shot her Fire Buster II at the Senshi, and stole the two Talismans. Those Senshi who were able to chased after her, and Eudial used the glue attachment on her gun to immobilize all of them except for Sailor Moon. Eudial and Sailor Moon battled, with Eudial easily overpowering her Moon Spiral Heart Attack. At this point Sailor Pluto appeared, revealing that she held the third Talisman (the Garnet Orb at the top of her rod). She returned Uranus and Neptune's Heart Crystals and revived them, and the three Talismans formed the Holy Grail. At this point Eudial used her Fire Buster on the Senshi and ran towards the Holy Grail in order to steal it. Sailor Moon broke through the flames and caught up to Eudial. Sailor Moon got to the Holy Grail first and transformed into Super Sailor Moon for the first time. The force of the power from Super Sailor Moon sent Eudial flying out the window of the Cathedral.
Eudial, battered and beaten, got back into her car and proceeded to drive back home to the Witches 5 laboratory at her usual unsafe speed. When she was about to turn a corner, Eudial hit the brake to slow down, only to find that the brake had been completely removed from her car, replaced by tons of snails (her worst fear) and a nasty note from Mimete. Mimete then broadcast a taunting message on Eudial's radio. Eudial was unable to control her car and it broke through the guard rails, careening over a cliff and landing in the ocean.
- Fire Buster - Eudial attacked using a flamethrower that she had invented.
- Fire Buster II - A more advanced version of the first flamethrower.
- Eudial is named for eudialyte, a red silicate mineral.