Before the events of the game, Aqua was awakened at her alter by Aster and Richter. They told her that they formulated a hypothesis that monsters were the ones distributing the world's mana. She offered to guide them to the Ginnungagap so that they could persuade Ratatosk into restoring the balance of mana. However, thanks to Ratatosk's rage at man and elvenkind, he mercilessly kills Aster and that Aqua decided to side with Richter instead. After Richter killed Ratatosk, Aqua told him to destroy Ratatosk's core, only for it to be recovered by Tenebrae instead. Richter and Aqua had set out to destroy the core (which ended up being attached to Marta Lualdi) and to find a way to help Aster.
Aqua and Emil first met at Lake Sinoa Cave. When Emil had to go against Richter, Aqua had a monster drive him away, but was defeated thanks to Ratatosk's power. After Emil told her that Richter was injured by Lloyd, she agreeded into helping him and adressed him as "acceptable". Later in the Temple of Ice, Aqua was seen with Richter trying to kill Marta. It turned out that the Marta Richter thought he killed was a fake made by Sheena.
During the final chapter, Aqua prevents the group from getting to Richter. She engages them by turning into a three-headed dragon known as Ladon. After the battle, she was gravely wounded due to her taking the form and damage of a monster rather than controlling one. Aqua turned back into a Centurion's core, but Emil refused for her to be hatched immediately due to the tension from earlier. In the end, Aqua did get hatched and told Emil to live the life he took from Aster, as well as telling him that she would help in the task of making mana no longer needed for the world and to make a seal to the door of Niflheim.
- Aqua's voice was done by Yoko Honda in Japanese and English Dubbed by Wendee Lee.
- Aqua is Latin for water.