From The Heretic Knowledge Vault
Direct mind-to-mind communication, without recourse to the spoken word. The Ensigerum can use it, although Sara, at least, doesn't like it, for unknown reasons. Sarine and Sarna also communicate telepathically during their encounter in Saus, and Sarine uses it to rendezvous with Jon amid the crowds of Tsuirakushiti.
This is another of the spells that the Anilis-possessed Ian is able to use as it's never been used before. When he contacts Meji Hinadori in her elven prison cell in Praenubilus Astu, it's the first time we've seen it used over distances greater than line of sight. This is probably going to
end in fire have interesting consequences.
Telepathy doesn't seem to produce complete transparency to the participants' thought processes. Sarine succeeds in deceiving Sarna about her post-Saus plans during their telepathic conversation.