The mysterious girl Wein met in his childhood. She is gentle and kind, and Wein loved to spend time with her when he was a child. One day he promised to meet her at the usual time, but couldn't make it due to being busy with his father. When he finally got to the flower fields to meet her, she was gone. She left behind an ocarina, which he picked up and treasured. Wein kept regretting the day he couldn't keep his promise.
On his way to the Magic Academy per Maximillian's request, Wein enountered her in the grasslands. She was accompanied by Sereb, a wolf that protects her. Wein did not recognize her at first, and urged her to go to a safe place because marauder attacks were occurring. He and his party encountered her again at Agriss village which was being attacked by Yungs (Gevel monsters), but she had a totally different personality; cruel and with a malicious agenda. She was on the Yungs' side and fought against Wein's party. She had the ability to teleport, and retreated when they defeated the Yungs.
In her normal personality, she later saw that Wein still had the ocarina and remembered the song that she taught him. However, she was saddened by his existence, and wished him to not get involved with her. She ran away from him when he enountered her at the Burnstein lookout. She believed there was no hope for her life because of Gevas.
Wein's party found Arieta in her evil personality attacking Schwarzfalz village aiming for the ancient relics stored there. They fought and defeated her, but she acted like the nice Arieta and Wein couldn't bring himself to hurt her. She escaped using this weakness.
Sereb informed Wein that Arieta was hosting the manifestation of Gevas. Gevas could not be destroyed. Long ago, the ruler of the Growsians extracted the lifeforce of Gevas and divided the power between the two strongest Growsians, Venzern and Arieta. She, like Venzern, is a Growsian born on a full solar eclipse. The fusion of her soul with Gevas was in process, and had to be stopped before it was completed. If it did, Arieta would become like Venzern; her personality would be completely taken over by Gevas and Gevas would revive. Sereb requested Wein to kill Arieta in her vulnerable state before it was too late.
Gevas occupied Arieta's body for more than two hundred years. Arieta had slept in the ruins northwest of Rottenbaum. From being weakened from long slumber, she would venture outside once a year for only three days. On one of those days she happened to meet Wein ten years ago. While Arieta was under Gevas' control, she had given up hope. Her meeting with Wein gave her a small glimmer of hope, but she feared it was futile.
Arieta (while possessed by Gevas) came to the Dimensional Fusion Control Tower to return to Gevas' true body. Gevas wanted to take back his world from humans. Gevas' soul transferred from Arieta to his own body and left Arieta's body lifeless. Gevas also took Arieta's soul, holding it hostage so that she would die if Wein destroyed Gevas. Wein came up with the idea of using the neural device from Ariost to communicate with Arieta's soul. The transmission device in the tower could call directly to people's hearts. Sereb offered to attach the device to Gevas. Wein convinced her that it was possible to save her and gave her a strong desire to live. She was restored to her body and she joined Wein's party to defeat Gevas. She wanted to help him as much as she could because he saved her life, and continued to accompany him.
In the era that she was born in, she fought in the war against Featherians by using Neural Armor (spiritual armor). She recognized the same armor being used in the fight at Comsprings.
Arieta will die if her soul is not rescued from Gevas in the fight against him.