Pengyon are colorful creatures that have some physical fish traits. They have a blue back and head, orange cheeks, an orange and pink chin, blue and green fins on the back, green flippers, and a white belly. A pengyon farm is located in Yseult and their native area in Maclir Beach just east of it. A variety of food is made of pengyon meat, which Eleanor Hume describes upon the group's first encounter with the pengyon.
After the events at Mount Killaraus, a talking pengyon appears in Yseult when evening comes. When Velvet Crowe and her companions rest at the town inn, they set out into the town during the evening to investigate the rumor. They soon discover the pengyon in question, and during their conversation, Eleanor slips up about eating something that talks, and the pengyon is enraged, turning into human and attacking the group.
The human loses the fight and reverts back into the pengyon. The two parties quickly make up and explain themselves. From the pengyon, they learn he is actually the human-turned-pengyon Jude Mathis from the distant world of Rieze Maxia, who, under mysterious circumstances ended in Yseult. When he came to, the local pengyon had accepted him without question, and he began to protect them from poachers as a way of repaying them. He also reveals he came with a friend of his, whom he believes has also turned into a pengyon: Milla. When Jude mentions she is a "Lord of Spirits", it catches the group's attention.