Aer is produced by springs called aer krene, and its levels on the planet are controlled by the Entelexeia. Aer is unable to be seen or felt when it is in a low quantity, but in a dense quantity, it is visible, and has adverse effects on health. In Tales of Vesperia: The First Strike, a highly concentrated area of aer is usually reddish in color and has effects on the environment, including the behavior of monsters. When a person is in contact with dense or concentrated aer, their body's metabolism accelerates. This causes fatigue and head pain. Prolonged exposure to dense quantities of aer may result in loss of consciousness.
When plants are exposed to a large quantity of aer, they grow to colossal sizes. An example is the state of Keiv Moc when the party first visits it in the story. Aer also has negative effects on monsters, generally causing them to panic and stampede. As a means to eliminate the calamitous Adephagos, Rita Mordio invents a formula which combines aer and the power of the four elemental Spirits. She forms a substance called mana, which is closer to matter than aer and far more safe.