Fire In The Sky
The use of psionic powers draw up and channel powerful energies from the higher dimensions. While ordinarily human minds contain such a low amount of energy that they do not stick out to psionic creatures or extra-dimensional entities, after using a psionic power, the user’s mind is left glowing white-hot, like a piece of metal that has been sitting in a furnace, a glaring beacon inviting the attention of everything nearby.
Additionally, to access the powers of the higher dimensions, the user’s mind must temporarily slip partially into these dimensions. It does not immediately slip out once the power has ended, exposing it to whatever may be going on in these distant planes at the time. Needless to say, the effects are not always beneficial.
Each turn that a creature’s mind is exposed, the GM rolls to see if it suffers any adverse effects from being exposed to the forces of the higher dimensions. Most of the time, there will be no potential effects. At least, nothing that you can see. However, rarely the user may encounter anomalous conditions, disastrous energy feedback, or malevolent entities. What might happen in that case, I leave up to your imagination. Needless to say, it usually won’t be good.
Additionally, even if there are no negative effects from the higher dimensions, exposure also leaves a creature much more vulnerable to the psionic powers of other creatures. Many psionic powers have additional effects against exposed creatures, or can detect or target exposed creatures at a much longer range. In the case of extremely psionically powerful creatures, an psionic enemy who becomes exposed is a sitting duck and a plaything. Beware.
In some cases, a creature using a lot of psionic powers may rack up exposure from multiple sources at once. In this case, each round of exposure occurs consecutively, not concurrently. That is, if a creature gets 3 rounds of exposure from one power, and 4 rounds from another power, then its mind will be exposed for 7 rounds, not just 4. You can’t be “twice as exposed” for 4 rounds. Each extra round of exposure just gets added to the total duration.