Psi crystals

[Alleine]

Do they get their own stats rolled up, or do they have the same stats as their owner? (with the exception of str and con)

The expanded psionics handbook leaves some explanations to be desired.

[Nebo_]

They have an entry in the monsters section of the XPH. I believe the progression lists Int increases.

[Alleine]

Yes, the psicrystal gets increases in int and AC as you level, but what about it other ability scores? Or should this just be house ruled?

[NEO|Phyte]

Use the Psicrystal (http://www.d20srd.org/srd/psionic/monsters/psicrystal.htm) stats, modified as needed to fit your character. The stats can also be found in the XPH, page 207