I could never figure out whether mages and thieves are supposed to be able to use these stones or not. Sometimes the game will let my mage use them, but other times not. What are the official rules regarding this?

Thanks [img]smile.gif[/img]

In AD&D 2nd Edition Ioun stones are usable by everyone

they are usable by everyone. it might not let you use them due to something with the multiple negative ac modifiers with armor and such, but other then that theres no reason why u cant use them, I love them myself how cool is it to have a stone floating around your head making you faster or stronger or whatever

most ioun stones are usuable by anybody. a few are restricted to a particular class, but their powers are usauly such that nobody outside that class would desire them anyway.

bug with ioun stones (and why mages were not always able to wear them). due to a bug in the infinity engine, anything in a head-slot protects from critical hits, since the head-slot was originaly helmets-only. ioun stones were added later, but this behaviour is still hard-coded. this is a way for mages and monk to avoid critical hits. whether this is good or bad depends on if you want to cheat or not.