Pymon destroys everything in her way and proclaims herself as the strongest Demon God.
Pymon was one of the Demon Gods who ruled over Demon World alongside Andras, Crosselle and Bellial. Although Pymon lost her body from being defeated by Lilith and Erina, she is awaiting the chance of rebirth by reincarnating in the body of demons.
The reason why Pymon, who proclaims herself as the strongest Demon God, possessed the fragile girl Reynai is due to her innate mana. As most demons who become hosts to Demon Gods do, Reynai was also born with an enormous amount of mana. On top of that, Reynai was also bright. She was considered a gifted child and everyone had high expectations of her. All because the adults said she should become someone great, she was educated strictly and rigorously. Such overbearing environment constrained her from expressing her opinions and made her a reserved, passive child. Reynai became the well-behaved, kind child her parents wanted, but everything completely changed when Pymon possessed her.
As soon as Pymon reincarnated through Reynai, she began to destroy the center of Saul. Though Reynai trembled at the unaccustomed power and violence of a Demon God, at the same time, for the first time in her life she felt a sense of liberation. Lilith arrived immediately upon hearing the news and stopped Pymon, sealing her in Reynai's body. From there on, as she did with the other Demon Gods, Lilith spoke of the 'Time of Ruin' and suggested a contract of obedience. However, she faced an unexpected obstacle. Contrary to her expectation that simple-minded Pymon would accept the contract without much thought unlike the other Demon Gods, Pymon who simply did not understand the content of the contract rejected it and started off. Even Reynai's all-nighter explanations were of no avail, so she had to take charge and proceed with the contract instead. Pymon, on the other hand, didn't seem to care what became of the contract.
Pymon thinks she and Reynai are the perfect team, a partnership of the strongest body and innate mana. Reynai seems to agree to a certain extent, but she becomes absolutely ashamed when Pymon starts flexing her muscles all of a sudden. The role of apologizing after vandalizing and causing harm is always Reynai's job as well.
There's a part of Reynai that admires Pymon who always acts with confidence. Especially when Pymon easily says things that she can't because of her timid personality, she feels vicarious pleasure and that she can depend on her. Now, as time has passed, she concurs with Pymon's destructive way of solution although she doesn't express it out loud. Sometimes she's the one who first suggests to Pymon that she run amuck.
Recently, to reduce the gap between Pymon and Reynai's personalities, Lilith suggested that the two should switch hobbies. That is how Pymon came to start embroidery while Reynai learns martial arts. Perhaps the new hobbies were a good fit, Pymon surprisingly won the Artist of the Year Award at the Demon World Embroidery Exposition, and Reynai made Celine cry in a friendly sparring match.