Nereid

Nereid (ネレイド) is a deity and, alongside Shizel, the primary antagonist in Tales of Eternia.

Past
Prior to Eternia's existence, there was the spirit world Vatenkeist, which was without substance and therefore not material. Nereid was a god of destruction, unmatched until the arrival of Seyfert, who sealed Vatenkeist within his own creation, the world of Eternia, in the Seyfert Ring, which the worlds of Inferia and Celestia support. Two-thousand years before the beginning of the game's plot, Seyfert sealed Nereid himself in Regulus Knoll of Inferia, the world that views him as a chaotic deity, while in Celestia, he is instead known as a brave warrior who fought against oppression. It is unknown how these different views came about, but they provide some evidence that Nereid is not necessarily pure evil, nor Seyfert pure good.

Ten years prior to the game's plot, Nereid managed, inexplicably, to break the seal that held him within Regulus Knoll. He makes his way to Rasheans, where Norris Oersted became his first host. Nereid mutated the man into a monster and tracked down three children who had previously been to Regulus Knoll who were now in Rasheans. He reduced the village to rubble and killed countless people before Norris was killed, forcing Nereid to leave.

Eventually, however, Nereid made his way to Celestia and found a woman there, Shizel, whom he blessed with his fibrill, as well as her blood relatives: her brother Hyades and her daughter Meredy. This feat was fairly easy for him due to Shizel's broken spirit following the loss of her husband, Transon Balir, who died in her arms. Her hatred for his killers then translated into a hatred of the entire material world, which coincided well with Nereid's desire to free Vatenkeist once more. Perhaps induced to learn the Dark Aurora artes more properly, Shizel, now Nereid's host, performed cruel experiments on Hyades and Meredy.

Role in the Plot
Over the years, Nereid gathered enough power to increase the dark matter surrounding his homeland, Vatenkeist, in the Orbus Barrier. Dark matter increases the gravitational force between the two worlds of Inferia and Celestia, spurring the Grand Fall. Both Nereid and Shizel seek to fulfill the Grand Fall so that the material world of Eternia will be destroyed and Vatenkeist released from its seal. Even in Regulus Knoll, where Nereid dwelt while sealed, his aura, or perhaps even his anger, remains despite his absence. When Meredy arrives at the seal, she roars words that do not come from her, instead coming from Nereid, who condemns Seyfert.

Physically, Nereid appears in Shizel's last form in the final fight of the game. At this point in time, his power begins to mutate Shizel into a monster, as she had done with Hyades prior. Upon defeat, Nereid leaves Shizel's body, but his fibrill remains with her, allowing Shizel to continue using her Dark Aurora artes to aid the heroes with the last of her power. This results in the destruction of the Seyfert Ring's core, separating Eternia from it. After this, Nereid's force kills Shizel. What happens after the destruction of the Orbus Barrier with Vatenkeist and Nereid in unknown.

Trivia

 * Together with Shizel, Nereid appears in the Coliseum in Tales of Vesperia, but is summoned by her only briefly when she attacks in close combat.

Nereid