From my 12 year old son, another of his creations-
This item appears as a small but incredibly valuable amulet, usually of platinum, mithril, or other very valuable metal with one flawless rare gem of great worth, that has strange engravings on it.
When worn, it gives the effect of a Mind Blank spell at all times and the wearer always gets a saving throw against illusions (even if the character has no reason to believe the illusion is not real). Furthermore If the creature wearing it is psionic, then all psionic strength points are increased 50%.
However, this blessing comes with a curse: every dayat dawn the wearer must make saving throw vs. poison at a +2 or roll on the random insanity chart.
If insanity is indicated, roll a d20; on 1-19 that is the number of days the character remains insane. If the result is a 20, roll again; a 1-19 on this second roll is how long the insanity lasts, but if the second roll is also a 20 the insanity is permanent.
The character does not need to roll for insanity if he is currently insane.