Vis Rules

My rules for Flavoured Vis appear in Mythic Perspectives, Issue #5. Below are additional rules used in the Thorendon saga.

Identifying Vis

While it is not difficult to sense the magic contained within vis, determining what kind of magic is not always easy. The most powerful kind of vis can be used in any magical activity, but most vis is only useful in certain situations. Vis of this kind has an "affinity" like the Virtue of the same name, and can only be used in magical pursuits that involve that affinity. Ie, some vis might only be useable in spells that involve ghosts, while others might be useful in all Mentem purusits. The more specific the affinity, the less useful (and more common) the vis.

In the Thorendon saga, magi can identify whether an object contains raw magic by making a Magic Theory roll of 12 or higher. A roll of 15 or more also allows them to determine the quantity of vis. To identify vis in this way requires handling it, and a few moments of concentration, but it does not require a spell. This can be attempted only once by a magus until he takes the vis to his lab (below).

Determining the nature of vis is slightly more difficult. The magus needs access to a lab for a few (roll stress die; a roll of 0 means only an hour or two) days. At the end of this time, he can correctly identify the quantity of vis, and must roll another stress die, adding their Magic Theory score + Int. If the roll is greater than 15, they can determine the affinity of the vis.

This method can be used only once by a single magus until he improves his Art or Magic Theory score. If the magus botches his identification roll, he either identifies the vis incorrectly, or is incapable of ever identifying it without an Intellego Vim spell (Storguide's decision). The SG may also decide that unusual types of Vis (from faerie or Infernal sources) are more difficult to identify than normal.

Identification of Vis
Detecting Vis Roll	Result	Identifying Vis Roll	Result
less than 12	no effect	less than 15	no effect
12 or greater	vis detected	15 or greater	Affinity detected
15 or greater	# of pawns

Detect Vis Roll = Magic Theory + Int + Stress Die
Indentify Vis Roll (lab required) = Magic Theory + Int + Stress Die

Some magi have invented, or use spontaneous magic to cast, spells that identify vis on the spot. These spells are usually InVi spells of the 3rd Magnitude, and are not always accurate when used on less poweful vis (which are more likely to vary from Hermetic norms).

The spells, Gather the Essence of Beast, and Alter the Nature of Vis do not exist.

Magi debate whether vis extraction (as described in the 4th ed) is actually possible; as yet, no one has been able to convince the Order they have discovered a reliable method of extracting vis from auras.