Complete Psionics Handbook[]
Not a proficiency in the Psionics Handbook.
Player's Option: Skills & Powers[]
Mental Armor: This proficiency allows a character to improve his mental armor class (MAC). Each time this proficiency is placed in an available nonweapon slot, the character's MAC improves. Nonpsionicists improve by +1 for each slot; psionicists improve by +2. The proficiency may only be slotted once per level advancement.
Dark Sun Campaign Setting Revised[]
This proficiency allows a character to improve his Mental Armor Class (MAC). Each time this proficiency is placed in an available nonweapon slot, the character's MAC improves. Nonpsionicists improve by +1 for each slot; psionicists improve by +2. This proficiency may only be slotted once per level of advancement.
Before receiving the benefits of this proficiency, a successful check must be made. If the check fails, the character must wait 24 hours before trying to engage his mental armor. Once the check succeeds, however, the MAC improvement is permanent. For more information about Mental Armor Class, see The Way of the Psionicist.