XP Cost (3.5e Variant Rule)
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To heavily limit the use of some psychic skills, the GM may require an XP cost in addition to (or instead of) the skill’s normal strain. Even a small XP cost (between 1 and 10) makes players more reluctant to use that psychic skill freely and a larger XP cost (100 or more points) makes the skill quite rare, since character’s won’t be able to afford to use it often. XP cost is best reserved for psychic abilities the GM wishes to confine to once in an adventure uses (at the most) and skills that may have a major impact on the campaign.