& Emergent Vis Sources
(DRAFT)

Vis Facility represents the tendencey of magical auras to produce vis. The Vis Facility of a magical aura influences how much vis that aura may produce, as well as certain modifications to the Aura Variation Rules given in RoP:M (10-12).

The Vis Facility of a magical aura is determined by adding up all of the tether scores that contribute to that aura (the base aura score referred to in RoP:M), and multiplying by three. This ratio is consistent with that given for vis sources in RoP:M (10). Note that the total tether score may not be equal to the current aura strength, in keeping with the Aura Variation rules in RoP:M.

Vis Facility may be compared with the annual quantity of vis that manifests in an aura. This includes all recurring vis sources, but excludes vis that is extracted by magi or others. Do not include quantities of vis that manifest temporarily, such as from aura variation results. Storyguides and Troupes may need to make judgement calls in the case of vis that is more irregular in its manifestion. This annual quantity of vis may be called the Annual Manifestation Quantity.

Compare the Vis Facility to the Annual Manifestation Quantity. If the Vis Facility is greater, there is more leeway for vis to be extracted or emerge. If the Annual Manifestation Quantity is greater (which generally happens only in situations of aura weakening, and then only rarely), then the effects of vis extraction may be more severe. The difference between the two becomes the Vis Facility Modifier. This modifier may be used with the Aura Variation rules given in RoP:M.

Vis extraction can inhibit growth of an aura, or even cause it to weaken (RoP:M, 10, sidebar: -1 modifier per season of extraction by a magus). There is one additional factor to add to the modifier for vis extraction activity. For each facultas aurae device with an *effect* level greater than third magnitude, which has been active for at least half the year, subtract an additional point from the aura modifier for vis extraction. This should be done regardless of whether the aura is strong enough to power the facultas aurae device. If several devices with sufficient effect levels have been active for less than half the year, but the total time is at least half the year, the combination should be counted.

Add the Vis Facility Modifier to the aura modifier for extraction of vis from an aura. This may reduce the penalty for vis extraction to zero, if the Vis Facility Modifier is high enough to counter the vis extraction activity. The aura modifier for vis extraction cannot become positive (i.e. it does not contribute directly to aura growth, only to aura weakening). However, if the aura modifier would have become positive, note the result, as this number represents the possible quantity of emergent vis (see below) that may manifest in the aura.

If the Vis Facility Modifier is negative, it makes the penalty for vis extraction more severe, and may contribute a negative modifier even in cases where no vis was extracted in that year.

Note that auras that manifest less vis are thus "resistant" to aura weakening due to vis extraction or powerful facultas aurae devices. Conversely, auras that manifest more vis are more vulnerable to aura weakening due to vis extraction activity.

Emergent vis is vis that may manifest in an aura when the Vis Facility Modifier is greater than the aura modifier for vis extraction. In situations of fluctuating aura modifiers, such emergent vis may be intermittent at first. If the Emergent Vis Quantity is one or more for a sustained period of time (generally, for around five years), then an emergent manifestation may become a new recurring vis source within the aura. Typically, the quantity of vis that manifests annually in the new source should be no greater than the lowest Emergent Vis Quantity over the previous five years. Emergent vis need not manifest as a single source: multiple sources, some emerging later than others, are possible and in many cases even desirable.

Emergent vis sources may correspond to the mystical properties of the aura, if appropriate. For example, an aura that is aligned to an emotion might manifest Mentem vis, whereas an aura aligned with a specific Hermetic Art might manifest vis of that Art.

Emergent vis sources may also arise from magically resonant activity at the covenant. Note that magically resonant does not necessarily mean spells or such. It could be that a superb craftperson's work generates vis in some manner, or that social gatherings within the aura generate vis somehow.

Also note that emergent vis is separate from temporary manifestations due to the results of aura variation (i.e. the results tables on page 11 of RoP:M). Because growing auras sometimes manifest vis in such a temporary fashion, emergent vis may not be recognized as such until its manifestation has been discovered and observed several times.

As an alternate to a newly emergent vis manifestion, a sustained Emergent Vis Quantity could simply increase the quantity of vis that manifests from an existing vis source. This is typically only appropriate for relatively small vis sources (one to three pawns annually), but in some cases may be appropriate for larger vis sources.