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Regina Babylon (レジーナ・バビロン Rejīna Babiron?) is the foremost genius of her time who created the Babylon Sisters, the Babylons, and the Frame Gears. She lived around 5000 years ago and was one of the citizen of the Partheno Sacred Empire. She is mainly referred to as Doctor Babylon (バビロン博士 Babiron Hakase?).
Regina is shown as a beautiful women in her twenties with long messy blond hair that extends to her waist while wearing round glasses and smoking a cigarette in her mouth. She wears a slovenly worn jacket and skirt with a white laboratory coat on top of it.
After her consciousness was transferred into a gynoid, she appears as a 10-year-old child with long golden hair reaching the waist and a pair of jade eyes.
She is a genius but also an erotic person. During her first met with Touya Mochizuki, she lifted her skirt and showed her favorite laced black panties. She likes to tease Touya with perverted suggestions and situations.
She is obsessed with creating new inventions and discovering new technologies to study, replicate, and improve. She is an avid mecha anime fan and watches the shows from Mochizuki's world for inspiration for Frame Gear weaponry and designs. She is very interested in the technology of Earth and is eager to learn how things work there.
Regina Babylon lived around 5000 years ago before the start of current story line. She was the most genius person to ever live in her time. Her lifelong rival, Professor Deborah Elks, a master of magic craft in Partheno, comes second with huge margin after her.
About 5092 years ago, she began to create the gynoid and the Babylon after seeing into the future through her magic tool. Through her clairvoyance tool, she found Touya Mochizuki and became invested in him. She then created the Babylon as her legacy to Touya while also creating 9 gynoids, the same number as the number of Touya's wives from what she saw in her clairvoyance, based on what she thought his preferences were (being mostly wrong). Unfortunately, a few of the gynoids turned out to be useless (Fam's refusal to stop reading when need, Noel's laziness and Parshe's clumsiness) or annoying (Cesca's blunt perversion and Tica's lolicon fetish).. The King of Partheno attempted to get Regina to take the Royal family and nobles into Babylon to avoid the Phrase; however, Regina rejected him in disgust, that he would abandon his people.  Rather than live out the rest of her days naturally, Regina had her brain removed and placed in the last gynoid, airframe #29.
Needing a lot of magic to activate her new near-immortal body, Regina had Atlantica set up a timer to force Touya to supply the magic; playing on his morality to save lives. Touya later found the Research Lab and did exactly what she planned, reviving Regina. Her immediate interest was in his smartphone, which she believed was a technology of the current era. Touya revealed that he came from another world, called Earth, which was far more advanced than the current world. After hearing Touya's warnings about the World Wars that world had, Regina decided to focus on more mundane technology to avoid endangering her world.
Currently, she spends her time creating new Frame Gear designs, weaponry and equipment, as well as recreating Earth technology, such as duplicating Touya's smartphone and making civilian vehicles, (automobiles).
In Interlude II, Regina caused mischief in Brunhild. Parshe found a magic transfer bag in the Storehouse and brought it to her. Regina used its [Apports] ability to steal the panties off Yumina, Lu, Elze and Yae among other girls. Touya realized what Regina was up to and quickly stopped her. To Regina's annoyance Yae (not understanding Regina wasn't the little girl she appeared as) spanked her as punishment. 
She later meet fellow scientist, Elluka, from the Reverse World, and began working on the Overframes with her to compensate for golem users in combat with the Golden Phrase.
Much later, in Volume 16 Regina offered to teach Sue about sex education, due to Sue's mother having not done so due to her years blind; Touya ensured the health book Regina planned to use wasn't weird, allowing her to teach the rest of the girls as well. However, it's implied Regina got carried away, as Touya heard one of the girls mutter "karma sutra" under their breath.
- Touya Mochizuki: Someone that she happened upon by chance through the use of one of her artifacts. She then designed and created the different Pieces of Babylon based on what she believed was his preferred preferences.
- Babylon Sisters: Specially created androids that were designed to control and maintain the different Structures of Babylon. They were loyal to her until Touya passed the Compatibility Tests; though they still get along. In the anime, Cesca admits she thinks Regina might be a bit crazy.
- Bride Conference: They tolerate Regina because she can be helpful, but dislike her perversion. Regina helped educate them about the birds and the bees; however, it's implied Regina went too far with her information.
- All Magic Attribute: She is another person that being introduced who has aptitude to all magic attribute beside Touya Mochizuki. Though unlike him, Regina naturally had all attributes; Touya was blessed by the God of Worlds.
- Analyze: Her personal Null Magic. It allows her to analyze the inner workings of any artifact she comes across.
- Genius Intelligence: She is perhaps one of the smartest mortal characters in the entire series, if not the smartest. She has created countless amazing artifacts that were far ahead of her time. Among her greatest creations are the Babylon Sisters, Babylon and the Frame Gears.
- Babylon Sisters: Androids Regina created to look after Babylon. She unfortunately caused a few of them to develop into perverts.
- Pieces of Babylon: Flying island, or kingdom Regina created for Touya's use.
- Frame Gears: Robots Regina built to combat the Phrase.
- Jewel of Future Vision: An artifact that can only show the glimpses of the future so long as there is someone who shared attribute affinity with the user. Unfortunately, it turned out to useless for anything practical to Regina as she only saw Touya's misadventures; due to him possessing all seven attributes like her.
- Reverse World Transfer Gate (versions 1 and 2): Devices to allow transport between the worlds once filled with Touya's magic. Became defunct firstly after Touya learned how to use his divinity to travel between worlds and lastly when the worlds merged into one.
- Various Frame Gear equipment
- Bride Exclusive Frame Gear types
- Various sex-related drugs
- "My Favorite" (「ボクのお気に入りだ」 Boku no Okiniirida?) - Regina Babylon when showed Touya her panties.
- Her android eye color is jade green in both the web novel and light novel, but red in the light novel illustration.
- In her original body, Regina has a bad habit of working until she tired her brain out. So she doesn't really remember things she invented.