A mindstone is in many ways the fusion of a power stone, an ioun stone, and a cognizance crystal. It stores a particular power, which a psionic manifester may later call upon as if he knew the power.
Physical Description: A mindstone is indistinguishable physically from an impression crystal, except that traditionally it is made of opaque stones such as opal, turquoise, and obsidian, and typically no smaller stones are included. These stones do not shed light except when used. It has the same physical statistics as a cognizance crystal.
Activation: The user must merely hold or have a mindstone on his person for a period of at least 10 minutes (which is long enough to attune the user to the crystal). After he has attuned to the crystal, the user who holds a mindstone in his hand may cause it to orbit his head as if it were an ioun stone. He may manifest the power stored within any orbiting mindstone as if he knew the power, provided the power is on his class list and he is capable of manifesting powers of that level. Unlike most psionic items, the manifester uses his own power points, manifester level, and key ability score when manifesting from a mindstone. Using a power from a mindstone is limited, however – a manifester uses his own manifester level or the power point limit of the stone, whichever is lower, to determine how many power points he can spend on the power.
A mindstone can hold any power with a power point cost equal to or lower than its power point limit, which is set during creation. For instance, a mindstone with a limit of 7 power points could hold the knowledge of any power of 4th level or lower, but the greatest number of power points that even the most powerful of manifesters could spend manifesting the power from it would be 7.
Storing a power within a blank mindstone requires a manifester to “lock” one of his powers known as unavailable for 24 hours, during which time he cannot manifest it (he is treated as not knowing that power for this duration). During those 24 hours, the blank mindstone must orbit his head continuously, drawing upon his sequestered psionic energy. At the end of this time, the power returns to his mind, and the mindstone is successfully attuned and is ready for use. If the manifester wishes, he may interrupt the attunement process by snatching the orbiting stone prematurely, which instantly restores his ability to manifest the power in question (although any time spent orbiting is wasted; the stone must be attuned anew).
Flushing a mindstone takes 10 minutes of continuous meditation. At the end of this time, the mindstone returns to its blank state, and another power can be stored within. An attuned wielder knows if a crystal contains a power, although he must address the mindstone (as if it were a power stone) before he can attempt to identify an unknown power within using Psicraft.
Construction: The market price for a blank mindstone depends on its power point limit, which is always an odd number and is never higher than 17. The formula is identical to that of a cognizance crystal: determine the highest-level power that could be manifest by spending a number of points equal to its limit, square this number, and multiply by 1,000 gp. For mindstones with powers stored within, the price fluctuates wildly and must be individually negotiated (if such an item is even available).
Faint to strong psychokinesis; ML equal to power point limit, Craft Cognizance Crystal; Price: see above; Weight