The Awareness skill allows a Persona to detect the presence or use of magic in the area.  Stronger magic may be detected at greater distances - the higher the Persona's skill rank, the more likely he is to be able to detect weaker magic, or magic at a greater distance.   The Awareness skill is based on the Aura (Empathy) attribute.
Each Origin is handled differently, and has its own special section below.  Several concepts do apply to all Origins, however.   First, all paradigms will have a "Noise Level."  This Noise Level is calculated in a similar fashion to Effect Level, but using Scope and Potency, rather than Potency and Intricacy.  Intricacy does not add to the Noise Level - an intricate but low potency effect with a narrow scope will be very hard to detect, although it may be a significant effect.
This Noise Level is subtracted from the Difficulty of any Awareness Trial.
Second, the difficulty of detecting an effect increases with range.  General guidelines for difficulty are as follows:
Difficulty Range
2 Touch
3 A few paces
4 A dozen paces
5 Several dozen paces
6 A stadia
7 A few stadia
8 A dozen stadia
9 A few dozen stadia
10 Over 50 stadia
11 Over 100 stadia
12 Over 200 stadia
Normally, only noisy effects will be detected at great distances, and then only by those with high skill ranks in Awareness.  A more difficult area to quantify is repetitiveness.  Just as a rhythmic sound will be more noticeable than a single noise, repeated magical noise in the same location will gradually become more noticeable.  The Mythguide should gradually reduce the difficulty somewhat, according to how far away and how often the repetition occurs.
Higher Degrees of Success in an Awareness Trial grant improved detail and/or accuracy to the sensing.  A Marginal Success indicates merely that something has been sensed, while a Complete Success might indicate a general direction, and higher successes would impart additional detail and accuracy to that.  The scale of detail should be balanced between the degree of success of the Awareness Trial and the distance to the sensed effect.
In general, the magical origins are handled differently from the deific origins.  Deific Omnessence use is much more difficult to detect using Awareness, although specialized paradigms may be developed to assist the Awareness user in doing so.  Such paradigms may also be developed to aid in the detection of non-deific Omnessence use - a few examples of such are detailed in the Paradigm listings for each Origin.


Mana use is the easiest form of magic to detect.  Because Mana is the underlying basis of Geozan reality, the alteration of that reality sends a disturbance through the flows of Mana.  Such disturbances can be sensed by anyone with the Awareness skill, and Mana users can even more readily sense them.  Use the standard guidelines listed above for Noise Level and distance, but reduce difficulty by one if the Awareness user possesses the Manasense Background Aspect (at any rank).


Sorcery is more difficult to detect than Mana use.  Only powerful disruptions of local reality will be readily detectable at any distance.  Use the standard guidelines listed above for Noise Level and distance, but add three to the final difficulty level (after subtracting for Noise Level - this means the minimum difficulty for detecting any Sorcery effect is three).  An Awareness user who lacks experience with Sorcery will often fail to recognize such disturbances for what they truly are, perhaps thinking them to be weaker manifestations of Mana use.


Spiritism is more difficult overall to detect than Mana, but is actually slightly easier to detect for those who possess the Sensitivity Background Aspect.  Use the standard guidelines listed above for Noise Level and distance, but add two to the final difficulty level (as with Sorcery, this may give a higher minimum difficulty).   Sensitives may subtract one-third (round down) their rank in Sensitivity from the final difficulty.  Additionally, of course, Sensitives may receive communication from spirits about what is occurring in the Spirit Realm, which may also give clues about Spiritism use in the area.


Alchemical effects are normally very difficult to detect, since they draw upon the natural mystical properties of things.   The process of refining or distilling such properties may be detected, however, in much the same fashion as Mana use.  Use the standard guidelines above to detect the active process of refining alchemical materials. 
Detecting the presence of alchemical materials using Awareness is possible, but not at any great range - double the difficulties listed above for distance.  Use the total amount of Potential Omnessence as the "Noise Level" for the purposes of detection.
Active alchemical effects may be detected as well, using the rules in the preceding paragraph, but in this case use the actual Noise Level for the effect, rather than the amount of Potential Omnessence.


Rune Magic
Rune Magic may be detected in two distinct ways - as the release of Alchemical essence which summons and directs the Runic spirit, and as the Spirit effect which has been directed by the Runic magic.  Use the respective rules for Alchemy and Spirit Magic accordingly.  Normally, this means that detection of the Spirit effect is the more likely, but someone experienced with Alchemy (and who is close by) may be more likely to detect the Alchemical release.  Such a release, of course, will only indicate the activation of a Conjuration / Spirit effect.


Necromancy can be very difficult to detect - the release of death energies upon which Necromancy draws is a "natural" part of Geoza, and therefore deaths cause only small ripples in the flows of Mana - such things are everpresent, and therefore rarely noticed.  An odd disturbance does accompany Necromantic access of the death energy, however, and this odd disturbance can be detected at short distances.  Use the general guidelines listed above for Noise Level (substituting the amount of Necromantic power accessed) and distance, but double all difficulty numbers for distance.  Only a highly experienced Awareness user will be likely to detect such a thing, and may not recognize it for what it is.  Necromantic effects cause little to no disturbance at all, and are nearly impossible to detect without specialized detection paradigms.


Deific (Generic)
Deific omnessence is not normally detected by use of the Awareness skill, but may be under certain circumstances - if the deific omnessence is in any way interacting with an existing or potential magical effect, then the alteration to that effect may be noticed (basically, most deific paradigms affecting the Reality dominion should in some way fall into this category).  Deific omnessence may also be detected if it is directly affecting the Awareness user himself, or someone / something to which he has established some sort of mystical connection (including using psychic powers).  Otherwise, the general use or presence of Deific omnessence is not detectable without the aid of specific detection paradigms.


Although Psychics technically do not use "Omnessence," and therefore do not use the Reality rules, the use of psychic powers can sometimes be detected with the Awareness skill.  Psychic powers do not use the game mechanics of Omnessence use, but conceptually, like everything else that is a natural part of the world of Geoza, psychic powers exist because of Mana.  Some Awareness users have developed a specialized sense for how the Mana is "disturbed" by the use of psychic powers in the vicinity.  The range of this sense is much reduced compared to other uses of Awareness, and developing this sense requires careful training in an environment of constant exposure to psychic powers, but it can be achieved by talented individuals.  Awareness users who have developed this rarified sense for psychic powers may also use specialized detection paradigms to aid them in doing so.


Detection Paradigms
In general, detection magic in Geoza functions as an aid to more mundane senses - few paradigms will allow a simple "yes or no" type of answer to a detection question.  Detection paradigms to help with the Awareness skill are a good example of the Geoza approach to detection.  Using an appropriate paradigm to help the Awareness skill adds a bonus to the ATC for the Awareness skill, but will not give an automatic answer to the adept using the paradigm.