Kephera should have a language imo. Something like the rattle language in Achaea, since I picture Kephera having clicky mandibles.

Everyone should have the ability to speak "nonsense" without the ability to understand it, however because illithoid understand language psychically they are the only people who can understand what those people are saying.

Kephera do have a language. It's called buttglow semaphore >_>