What happenned to Laurin's ioun stone ?

[Jaxzan Proditor]

Yep, mana, or mp
Crystals probably refers to one of two things:
psicrystals are animated crystals that work like a wizard's familiar.
Cognizance Crystals are items which store extra psionic points in them.

I see. Thank you for the links.

[rodneyAnonymous]

Yes, like mana, you can spend power points to "cast any spell you know" (manifest any power you have), which have variable point costs, until you run out of points. Psions are more like sorcerers than wizards, but spending points instead of spell slots makes a big gameplay difference.

Another major difference is that psions can choose to spend more points than the minimum casting cost to augment some powers in different ways, often simply making the numbers bigger.