WEG's d6 Space game system treats psionic effects differently from most other games I've tried. It is somewhat freeform, allowing the player to construct an effect from scratch. Each component of the effect has a difficulty modifier assigned to it and the sum of all these modifiers determines the overall difficulty. That difficulty is then compared to one of three metaphysical skills (the term "psionics" is not used, in favour of "metaphysics") which most closely describes the effect. The skills are channel (used for physical attacks, defense and other related effects), sense (anything related to detection) and transform (a catch-all skill that describes anything not covered by the other two skills, such as healing, telekinesis and teleportation).