Scaling Psionic Monsters

[CIDE]

In the same vein as the other thread I recently posted I'm inquiring on behalf of not only myself but other curious players. This is likewise for the same sandbox Multi-DM style world I mentioned in the other thread. Characters are stared at level 20, a few higher NPC's running around, etc. I was working on tweaking some monsters and experimenting with template stacking on conventional monsters to get them to be a threat to level 20's (mostly the shock value of an owl bear still being a threat to a level 20 fighter). Anway! This time I'm dealing entirely with psionics.

I'm aware of creatures like the Illithid and the Unbodied. They both manifest as a psion of X level of..I believe both telepath. I also know that the gem dragons have a similar style that simply grows to a cap depending on their age. My question to you all, though, is another type of psionic manifesting in D&D.

Are there creatures that Manifest as X (say a psion) but base it off their HD? Things like the Phaerimm casts spells as a Sorc of their HD. Likewise a Spellweaver does something similar. Are there any manifesting creatures that do something similar? Is there an advanced Y monter out there casting as a level 20 Psion.

Homebrew isn't off the table but I'd like to avoid it at all possible.

[Eldariel]

This compendium (http://brilliantgameologists.com/boards/index.php?topic=5514) lists no such monsters, though Cranium Rat Swarms come in a variety of sizes and it isn't difficult to piece together numbers for larger swarms for greater manifesting prowess.

[Ashiel]

In the same vein as the other thread I recently posted I'm inquiring on behalf of not only myself but other curious players. This is likewise for the same sandbox Multi-DM style world I mentioned in the other thread. Characters are stared at level 20, a few higher NPC's running around, etc. I was working on tweaking some monsters and experimenting with template stacking on conventional monsters to get them to be a threat to level 20's (mostly the shock value of an owl bear still being a threat to a level 20 fighter). Anway! This time I'm dealing entirely with psionics.

I'm aware of creatures like the Illithid and the Unbodied. They both manifest as a psion of X level of..I believe both telepath. I also know that the gem dragons have a similar style that simply grows to a cap depending on their age. My question to you all, though, is another type of psionic manifesting in D&D.

Are there creatures that Manifest as X (say a psion) but base it off their HD? Things like the Phaerimm casts spells as a Sorc of their HD. Likewise a Spellweaver does something similar. Are there any manifesting creatures that do something similar? Is there an advanced Y monter out there casting as a level 20 Psion.

Homebrew isn't off the table but I'd like to avoid it at all possible.
There's really not that many psionic monsters, mostly because there's less support for psionics than for regular magic. But there is enough material to help GMs understand how the existing ones are engineered. Even if we ignore things like the Phrenic Creature (http://www.d20srd.org/srd/psionic/monsters/phrenicCreature.htm) template, other monsters can be comfortably converted (such as replacing a rakshasa's spellcasting with manifesting).

And naturally there is always the option to simply add class levels to monsters. Most creatures get a "discount" of sorts when it comes to adding non-associated levels to them, and a lot of monsters can easily make use of things like feats to boost their effective manifester level, or have unique synergies that combine well with a bit of manifesting.

A psionic troll might readily enjoy the Overchannel feat since their regeneration will take care of the damage it deals to them. Psicrystals base many of their statistics (such as HP) on their owners, which means that racial HD can contribute to some of their statistics.

Many monsters really don't need a lot of manifesting to make them a more credible threat. I ran a short game for some friends involving the exploration of a pyramid. It had some mummies with a few levels of psychic warrior. This gave them access to powers such as expansion (+size increase), bite of the wolf (+bite attack), inertial armor (+4 AC), and specified energy adaptation (+fire resistance). Their bite of the wolf was fluffed as jackal heads, and of course all of these things had natural synergy with the base vanilla mummy.

[CIDE]

Thanks for the answers. Nothing that really helped at all, though. Mostly stuff I was actively trying to avoid (I.E. just tossing in class levels) to get to where I was going. Oh well. I was kind of expecting this given the lack of psionic support.