Malty S. Melromarc

"Please don't do anything as foolish as to look for revenge. Revenge only breeds further revenge. If you, Mr. Naofumi, could bear to show mercy, then I'm sure the queen would be grateful."

- Malty begging for Naofumi's forgiveness (only to be refused)

Former Princess Malty S. Melromarc, later revealed to be a soul fragment of Goddess Medea Pideth Machina, and also known as Mein Sophia as her (previous) advanturer name, and later "Bitch" as a spiteful derogatory given by Naofumi, is the main antagonist of The Rising of the Shield Hero.

She was voiced by Sarah Emi Bridcutt in Japanese version, and by Faye Mata in English version, with the latter also voiced Yumemi Yumemite in Kakegurui.

Overview
Malty Melromarc is the former eldest Princess of Melromarc, and the eldest daughter of King Aultcray Melromarc XXXII and Queen Mirelia Q Melromarc, and the archenemy of Naofumi Iwatani, the titular Shield Hero.

Being the former first Princess of Melromarc, Malty was the first person to join Naofumi in the beginning, but it was revealed to be a ruse to steal his money and equipment except her shield. She also framed Naofumi and turned him into a criminal at large, turning him into a darker and pessimistic person.

She was later revealed to be one of the fragments of Medea Pideth Machina, a self-proclaimed goddess originating from another world, who caused the waves by merging together eight separate worlds. Her goal is to drain each world of its energy for her own use, while enjoying the suffering of all the inhabitants inside.

History
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Fragment - Malty Melromarc
In spite of her beauty and pretentious kindness, Malty is in fact a greedy, opportunistic, selfish, ungrateful, manipulative and treacherous liar who always treats deceiving, manipulating and insulting others as a hobby. She never shows true loyalty towards others, and will use and betray others as soon as she get a chance. Her personality was apparently caused by being spoiled by her father

Due to her traitorous nature, Malty is the catalyst of every bad events in the story, including Naofumi Iwatani's turn into the dark side and his false infamy. She is directly responsible for each of the Four Heroes unlocking their Cursed Weapons, indirectly renders Motoyasu permanently insane, and caused her father's decline from the Wise King to Trash.

Besides her deceitful nature, Malty is also an uncaring person to the people in her kingdom and even her own family. According to her mother, Malty always hides in the shadow and enjoys bringing misery to others. Naofumi was so disgusted by this information that he immediately dubbing her as "Bitch" (or "Witch" in some translations). She goes as far as to use the countries treasury for her pure enjoyment of a hedonistic and luxurious life, even calling it "for the sake of the world." She also levying heavy tax on the wave damaged village calling it for reconstruction.

In a nutshell, Malty is a hateful consummate deciever who is fond of trample those who trusted and loved her to reach her own goal. Given a chance, she will bite the hand that feeds her. Even her own family was no exception.

True Form - Medea Pideth Machina
In the final arc of the web novel, which the light novels, manga and anime are yet to adapted, Malty is revealed to be a soul fragment to a self-proclaimed goddess, known as Medea Pideth Machina, who is even worse than all of her fragmental counterparts.

Much like her fragments which work to sabotage the heroes and ensure her Waves of World Fusion go uninterrupted, Medea is a rotten, hateful, selfish and remorseless God Wannabe in the core, believing human are just her tools for her to manipulate and admitting everything she did was all for pure enjoyment. She has no attempt of repentance over everything she did. Instead, she boasted her atrocities proudly and had no regards over anyone she trampled underfoot, including Naofumi and later Glass.

Besides, Medea is just as manipulative and deceitful than her fragmental counterpart, Malty. She and her fragments managed to convince many reincarnated people that she's "good" while sowing discord and death. This act is so convincing that even when she's perpetrating horrific atrocities right in front of them, and confessing to many other crimes, the "heroes" that follow her still think she's the epitome of righteousness.

One of her crueler tactics is to bring back the soul of a deceased enemy and send it to their former allies, claiming to have survived their apparent death. After fighting on their side for a short time, the soul will take advantage of an opening to betray them.

In the end, Medea reveals her plans to extinguish all life in the universe one world at a time simply to boost her power level, before flying into a rage when beaten and simply trying to take down millions with her as she dies. Ultimately, Medea is revealed to be a self-proclaimed sadist who committed her crimes for nothing except greater power, and she always commit atrocities with glee and pride.

Trivia

 * Malty is similar to Rize Kamishiro from Tokyo Ghoul. They both pretended to be sweet and kind women who made the protagonists to fall in love/befriend them, before trying to take them down when they revealed their true nature. They are also responsible for the formation of the protagonists' darker personality and tragedy.
 * Interestingly, the respective Japanese voice actressess of Melromarc Sisters also worked together in Date A Live anime series in voicing Yamai Sisters. The voice actress of Malty, Sarah Emi Bridcutt, voiced Yuzuru Yamai, and the voice actress of Melty (Malty's younger sister), Maaya Uchida, voiced Kaguya Yamai.