Web Novel Edit
Described to appear as a dog but is in fact a being closer to The Thing in disguise where her creator deleted the ability to transform like she should as a Heteromorph of her race. 
When Demiurge mentions having trouble working with Sebas in the Web Novel Men in the Kingdom arc, he states he feels he could work better with Pestonya despite being polar opposites than he can with Sebas. 
An interesting thing to note, just as Eclair is somewhat excused for his treasonous words due to that being programmed in him as flavor text , Pestonya was not viewed as harshly in the Light Novel for saving the human children due to having kindness programmed into her, barring Albedo's view on her and Nigredo's actions  
- ↑ Volume 4 Author Thoughts: By the way, the two titans of kindness are Pestonya and Mondenkinto from the WN, Who is it? Because Mondenkinto-san’s is a masterpiece of a character in the story, it will not be revealed in the book publication.
- ↑ After Chapter Notes Arcadia: Note: Pestonya is a heteromorph. The ability to transform like The Thing [lit. the Japanese title of the John Carpenter version] was deleted on the creator’s side, is how things are [now].
- ↑ Web Novel 74: That was how bad Demiurge and Sebas worked together. It was to the point that he felt that he could work better with Pestonya who had the complete opposite personality. He had confirmed that he could not work well with Sebas.
- ↑ Volume 2 Intermission: It was widely-known that Eclair hungered after the throne of the Great Tomb of Nazarick. He was a creation of the Supreme Beings, so he was beyond question. Of course, if the order was given, Demiurge would eliminate him without mercy, but until then, he had no objections.
- ↑ Arcadia 2459: Nazarick has a narrow view on loyalty. The it’s like a madman’s devotion, it ought to be painful to an ordinary person don’t you think? Pestonya’s gentleness exists in her settings. Because the 41 Supreme Beings made her gentle, she is pardoned, for Sebas it differs.
- ↑ Volume 10 Chapter 1: "That will not be a problem. In all likelihood, nobody in Nazarick will object to freeing those two other than my previous self." "Is that so …then that’s good. Put the two of them in charge of running the orphanage."