Psychic Background Count
Psionics defy reality. They are the manifestation of the sentient mind's control over what is normally impossible. Each occurrence of psionics places a strain on the fabric of reality, warping it slightly. The effect is not visible, but can be sensed as a disorienting, disturbing feeling in an area. This warping effect is referred to as Psychic Background Count.
Usually, Psychic Background Count is relately low, placing a negligable effect on psionics. However, in areas of intense psionic activity, the fabric of reality has become so warped that psionics have a penalty to function there. The Psychic Background Count add to the Drain of psionic powers. They also causes maintained powers (even those maintained for free) to falter, forcing a re-roll of the powers against DC 15 plus the Psychic Background Count or be lost, inflicting Drain when doing so.
The penalty for Psychic Background Count varies, but usually is rather dramatic. For an area such as a psionic school where intense training has occurred over a relately short period, there may be only a Psychic Background Count of 2. For a huge battlefield where two psionic armies fought for a week, the Psychic Background Count would be somewhere around 10. Most areas are around 4, but even a single point of Psychic Background Count is of concern to psionists, and is to be avoided.
Psychic Background Count dissipates slowly, often lasting for weeks and even years. It is often exponential in duration, so the larger the Psychic Background Count, the longer it takes to dissipate. It also tends to spread to areas of nearby psionic activity, making even well-known areas with Psychic Background Count harder to avoid.
Psionic schools sometimes cause enough Psychic Background Count to inflict a penalty. Most responcible and good psionic schools keep a couple of locations and move periodically when they place a lot of strain on the area. A company employing a lot of telepaths in their central office may generate some strain after a few years. For the most part, though, Psychic Background Count is a phenomena which is pretty localized, and lasts for years, decades, or even centuries.