Cleon
Legend
Hmmmm. These are probably closer to the ceremorphs, so let's do the magic and psionic versions separately. But I might suggest revising some of the spell equivalencies to unique abilities. Mind thrust or psychic crush (or both?) could probably be replaced with something like a mind flayer's mind blast.
A phantasmal killer spell is pretty close to the 3E version of psychic crush. I'd be OK considering an alternative to mind thrust. I'd be OK considering an alternative to magic missile for mind thrust, but it seemed a neat match to the "counter-power" of shield in the proposal.
I'm not keen on spending much time on it, though.
What about the suggestions to increase the Con and/or Cha and possibly add Unholy Toughness to account for the original's high hit points?
There was no mention of Cessirids having especially good saves against poison or the like, so I'm currently leaning towards a higher Charisma plus Unholy Toughness.
Its highest level psionic power is psychic crush, which normally requires Cha 15+ to manifest, so I'm thinking maybe Cha 15?
That'd give it an additional 16 hit points with Unholy Toughness.