Psi-form

Psi-forms were creatures inhabiting the psychosphere of a planet.

Usually, Psi-forms were not directly perceptible to the matter-based inhabitants of the same planet but could influence their emotions. Special technology, such as headgear created by the Tenth Doctor, could reveal psi-forms and facilitate communication with them.

The most common psi-forms were Pranavores. On one planet, experiments on Pranavores led to the creation of psychosphere predators, Cerebravores. (COMIC: Revolutions of Terror)