The psionics system was greatly revised in "" and the revised "Dark Sun Campaign Setting". Psionic abilities are determined by a character's Wisdom, Constitution, and Intelligence scores. Any character with sufficiently high scores and some luck will have some psionic talent known as a "wild talent"; any player character in the Dark Sun world will have psionic talent. Characters have Psionic Strength Points (PSPs) and a Mental Armor Class (MAC); attacking involves expending PSPs, and making an attack roll against the target's MAC. The system was redevised around a Mental Armor Class (MAC) and a Mental THAC0 (MTHAC0), mimicking the Armor Class (AC) and THAC0 used in normal combat. The harder the power was to use, the lower the MAC was to activate it. Likewise, the harder a mind was to break into, the lower that person's MAC was. Psionicists would have MTHAC0 scores that represent their ability to wield the psionic arts. This was exactly 21 minus the level of the psionicist. Many of the powers were also altered in this revision.