The Caeliar gestalt was a shared mental link between Caeliar individuals, allowing for communication and transmission of ideas. All Caeliar, and any others whose bodies possessed catoms could access the gestalt.

When the Caeliar encountered the Borg, they found they could hear the thoughts of the Borg Collective, which was later discovered to be evidence pointing to their shared origins. (ST - Destiny novels: Gods of Night, Lost Souls)