All meta-human or otherwise super-powered characters will possess abilities which have a power modifier as introduced in GURPS Powers.
The following Power Modifiers are available to any character with a relevant power source/origin. They may also be used as the basis of creating a custom power modifier for your character.
-10%
Your power is a physical capability of your body. It's fatiguing to use because your metabolism must supply all of the energy: pay an extra 1 FP whenever you use an active ability (Costs Fatigue, 1 FP, -5%). Anything that upsets your unique metabolism might deprive you of your power – including targeted pathogens, drugs, and nanotech designed by your enemies (technological countermeasures, -5%).
For passive abilities, you must either add the Switchable enhancement, thus making it cost 1 FP to activate, or use a variant Biological power modifiers that is only -5% and excludes the 1 FP cost.
-10%
Your power emanates from your life force – a mysterious energy often called chi or ki. To strengthen your chi to the point where you can channel it for superhuman feats, you must engage in exercises and meditation for a few hours each day. This requirement is a -10-point disadvantage (-10%), most often Disciplines of Faith (Monasticism or Mysticism) or a comparable major Vow. Should you neglect this, your power fails you the first time you call upon it under stress (+0%). To restore it, you must take 1d days to rebalance your chi (+0%). Until you do, you feel ill; the GM should choose one of these afflictions from Irritating Conditions: Coughing/Sneezing, Drowsy, Nauseated, or Pain.
+50%
Your power originates from the energy of creation! Your abilities ignore the ordinary countermeasures that work against wild advantages, and you always have access to them – nothing can neutralize your power or cut off its energy source. This is identical to the +50% level of the Cosmic enhancement. If you have individual abilities with more expensive versions of Cosmic, your power modifier only covers the first +50% of their value; after that, you must pay for Cosmic normally.
-10%
A deity grants you your power. Nothing can prevent your god's power from reaching you… but your patron expects certain behavior in return. The precise details depend on your god.
A good god expects you to lead a virtuous life. The required moral code is a -10-point disadvantage (-10%), typically Honesty (12), Sense of Duty (Coreligionists), or a major Vow. Should you transgress, your god will suspend your power – but since he's benevolent, he won't cut you off if this would endanger you (+5%), save for the most egregious of sins. To make amends, you must offer significant penance: up to a month of fasting, questing, or equivalent (-5%).
An evil god lets you do as you wish, provided you make suitable sacrifices, corrupt the innocent, etc. These requirements are worth -10 points (-10%), most often in the form of Intolerance or a heinous major Vow such as "Kill someone on the night of the full moon." If you forget, your deity will revoke your power instantly (+0%). It will turn on you in horrible ways until you make amends (-5%). A single killing or desecration will get you back in favor – since you've already sold your soul, this should be easy for you (+5%).
An ineffable force of nature only rarely concerns itself with mortal affairs, leaving you free to act in its name as you see fit. But it has principles – often strange, confusing ones – that constitute a -10-point disadvantage (-10%), perhaps a Code of Honor such as "Respect nature, and violently oppose those who do not" or a complex Trademark that few can understand. It will immediately cut you off for any perceived improbity (+0%). To get back in good standing, you must complete a minor quest (+0%) suggested to you through omens.
-30%
Your power's abilities require weekly maintenance, at 1 hour per ability (-5%). In addition, they can be detected by X-ray scans and other forms of medical imaging, and may also generate radio static or an odor of ozone (-5%). Finally, they’re vulnerable to electrical disruption as defined for the disadvantage Electrical (p. B134; -20%).
-10%
Your power lets you manipulate an "element": one particular kind of natural matter or energy, or its absence. Examples include Air, Cold/Ice, Darkness, Earth, Electricity, Heat/Fire, Light, Radiation, Sound/Vibration, and Water. This power isn't psionic or channeled from an elemental god; powers like that are Psionic or Divine, respectively. Instead, you're cosmically attuned to your element; in effect, you are an elemental spirit.
The GM should choose a mundane countermeasure or insulator that can interfere with your elemental energy. Either way, this is worth -10%. If your element would not logically merit the full -10% for countermeasures or channeled energies, the GM may rule that this limitation is a little of both. It's fairest if every elemental power is more or less equally limited.
-10%
Your power channels ambient magical energy (mana). This is difficult to block and found almost everywhere. "No-mana zones" – areas where your power doesn't work at all – occur only rarely in nature. However, low-mana zones are more common, and all rolls to use your abilities are at -5 in such regions. This aspect of the limitation is worth -5%.
In addition, a variety of anti-powers can thwart your abilities. The Mana Damper advantage simulates the effect of a low- or no-mana zone, while Magic Resistance shields others from your attacks. Moreover, spells that dispel or protect against magic affect your abilities exactly as if they were spells. This is worth another -5%.
This modifier is identical to the Mana Sensitive limitation.
-10%
Your power's abilities require weekly maintenance, at 1 hour per ability (-5%). In addition, they can be detected by X-ray scans and other forms of medical imaging, and may also trigger metal detectors, smell of oil or exhause fumes, or get hot enough to show up on infrared (-5%).
-20%
Your power comes from some cosmic moral principle – Chaos, Evil, Good, Order, etc. – that transcends the mortal and even the divine. This isn't a true cosmic power… it's more like half a cosmic power, because it has an opposing anti-power (-5%): Chaos vs. Order, Evil vs. Good, and so on. This anti-power offers its wielders Neutralize and Static abilities (and perhaps other gifts) that they can use against you. Your power gives you similar weapons, of course.
Your ability to tap this power stems from your dedication to a moral code, to which you must adhere at all times. This is a -15-point disadvantage (-15%), usually Fanaticism – although Honesty (9) or Sense of Duty (Humanity) is just as likely for Good. If you falter, even for a moment, you lose your power instantly (+0%). To get it back requires an extreme demonstration of commitment that costs at least 2d days of lost time or earnings (+0%). Details are up to the GM, who should pick something appropriate to your power; e.g., a large donation to charity, for Good.
This modifier only exists in settings with absolute morality, where moral forces battle openly in the world and are both tangible and detectable.
-10%
Your abilities come from a genetic mutation. They may be counteracted by Neutralize and Static as wild advantages and as part of various anti-powers (-5%) and weird-science devices exist to block or even steal your powers (-5%). Mutant powers can be detected using DNA sequencing or similar abilities. They are also the targets of bigotry, but this is a separate disadvantage.
-20%
Your power channels the vital energy that surrounds all living things. This exists even in the driest deserts and on the most barren peaks, but the ravages of civilization interfere with it, acting as a mundane insulator against your power (-10%). You're at -1 to use your abilities in a despoiled wild place such as a clear-cut forest, -3 in a city, -5 amidst ordinary pollution, and -10 in a poisoned wasteland.
Technology – not technological countermeasures, but any technology – also impairs your power. In effect, it's a mundane countermeasure (-10%). You're at a penalty equal to half the TL (round up) of the most advanced manufactured item you're carrying, wearing, or riding in or on. Use the full TL of implants. Thus, a TL3 sword gives -2, while a TL8 pacemaker gives -8.
An ability that requires no die roll loses 10% of its effectiveness (bonus to reactions or skills, DR, etc.) per -1 instead. If the penalties total -10 or worse, you're powerless.
-10%
Your power is an innate capability of your mind. The energy comes from within, but a large number of countermeasures exist, including anti-powers in the form of Antipsi power (-5%) and technological countermeasures in the form of "psychotronic" or "psi-tech" defenses (-5%).
-10%
Your powers come from a state of intense concentration, which may be the effect of self-hypnosis, drugs, or biological peculiarities. While you are using them, you are totally focused on your own thoughts and perceptions. This gives you two temporary disadvantages: Oblivious, making it difficult for you to interact with other people (Temporary Disadvantage, -5%), and Incurious (12), making it hard for you to turn your attention to anything novel (Temporary Disadvantage, -5%).
-5%
Your power comes through commanding spirits: you give orders and the spirits do work. Since only those with powers of their own are likely to realize this, it's often hard to distinguish your aiblities from chi, psi, etc. For most Spirit-based powers, assume the spirits are not generally capricious and do not use fickle (as described in GURPS Powers).
Instead, you only have an imposed -5-point disadvantage (-5%) – typically Disciplines of Fiath (Ritualism), Sense of Duty (Servitor Spirits), or a simple Trademark in the form of a small offering or token. If you fail to live up to your imposed disadvantage, the spirits turn against you, depriving you of your power at the worst possible moment (-5%). It is easy, thought, to make amends – a minor sacrifice, such as a food offering, is usually enough (+5%).
For more capricious spirits, add fickle (-20%), and whether they answer your summons at all depends on an unmodified reaction roll. An individual ability might involve more or less friendly spirits, giving a modifier of ±4 to your reaction roll. If so, that one ability has an extra ±5% modifier per ±1, on top of the basic power modifier that applies to all abilities.