A Spiria (スピリア Supiria?) is a term in Tales of Hearts that encompasses a person's heart and emotions. At the core of a person's Spiria lies the Spiria Core (スピルーン Spiruun?, "Spirune"), guarded by a person's personal labyrinth called the Spiria Nexus (スピルメイズ Supirumeizu?, "Spir Maze").
In the world of Tales of Hearts, the Spiria is a representation of a person's heart and emotions, though animals can have Spirias too, and particularly gifted artists can create Spirias within their works. They can also be synthesized into mechanoids, though they are noted to be inferior to the real thing. To have a strong Spiria means to be self-assured and good, while a weak one succumbs to darker and baser emotions. A Somatic wielding the power of the Soma has the power to enter a person's Spiria and communicate with the heart within.
To do so usually involves traversing the person's Spiria Nexus, which may be filled with all manner of traps, and reaching the person's Spiria Core, which can manifest as a side of the person within. A Spiria Core is vital to a person's life; if it is lost or shattered, the person is rendered either comatose or without emotion, and death will follow not long after if the situation is not changed. When a Spiria is interfered with, such as through the infestation of xeroms, it manifests as the disease despir. On the other hand, when a Spiria is fully drained of its vitality, it leads the subject undergoing the process of calcification (白化 hakuka?, "whitening"), in which the person's body turns into white stone. The Spiria can also be bolstered by bonding with others through what is known as the somatic bond, which gives mutual strength to those united Spirias.
The existence and the manipulation of Spirias form the events of Tales of Hearts. Two-thousand years prior to the game, the world of Minera was a war-torn and hedonistic place where the upper class warred for sport. Fluora Spodumene wished to end the fighting through her global Somatic Bond plan by uniting the world's Spirias into one web and foster understanding. On the other hand, Creed Graphite and Lithia Spodumene supported the creation and deployment of Gardenia, the mother xerom who was to absorb the warlike emotions of Spirias to end the fighting. Unfortunately, Gardenia was patterned off of Creed, whose Spiria hid a desire the light and love that he did not feel, and so rather than just consuming part of Minera's Spirias, it devoured them all. It causes a mass calcification of all life on Minera, leading Fluora to sacrifice herself to seal it away before it could set it sights on the world of Organica. Creed wished to save Fluora and damn Organica while Lithia wanted to adhere to Fluora's wishes and lock away Gardenia for eternity, leading to Creed's and Lithia's millenia-long battle by existing as spirits traveling from Spiria to Spiria, something said to be impossible.
In the present time, Lithia takes residence in Kohaku Hearts's Spiria, while Creed is sealed within Kor Meteor's, without his knowledge. When Creed's power leaks during a Spiria Link by Kor into Kohaku, Lithia shatters her Spiria Core and hides in the scattered shards. Unaware of Lithia, Kor journeys to gather Kohaku's shattered Spiria, but when he succumbs to his darker emotions, he unwittingly revives Creed, who in turn unseals Gardenia in an effort to revitalize Minera at the expense of Organica. Kor's group enters Gardenia to stop him and discovers that, even after two millenia, the absorbed Mineran Spirias remained intact by forming somatic bonds with each other. Once freed from Gardenia, these Spirias fall to the calcified Minera and seed it with a hope for the future.