A typical wizard or covenant should have a store of Vis. This might be a few pawns, or may be substantial depending on the character age or covenant season. Allowing PCs to assign their vis is a good thing, but if it cannot be agreed, or if a random solution is desirable, try this.
While pondering the problem looked for (a) way to roll random numbers, (b) way to associate them to each art, (c) allowance for special types of Vis, and (d) allowance to alter how common each type is in the setting by applying a weighting or scarcity value.
As a starting place this could be a scratch pad with 1-20 written down, arts assigned a number, and a d20 in your hand. Pretty simple for one off needs. I decided to use a spreadsheet to do it, because it is a small task I’ve had to do many times and it keeps being a pain. This gave the flexibility to muck about with the weighting and determine a large amount of vis in one go.
Perhaps one of the days I’ll make one for spells and books too.
- Setup the spreadsheet to show each type of vis you want. By default the 15 types are present in mine, and there are 5 additional slots for other types should they be desired. My suss is realm aligned types, saga specific types, or perhaps hybrid types are there, they should be rare compared to the norm.
- Update the scarcity of each type. Some sagas make particular types rare and other common. e.g. If the magus goes gathering amongst the mountains an Aquam find should be unlikely, and Terram more common.
- Confirm the amount you want, but adding or deleting rows in the Random area. The sheet generates up to 40 without too much hassle; and adding more is easy as sliding the rows down.
- Copy & paste the result text into your summary, covenant, sheet.
Its as rough a spreadsheet as you’d expect, but it works. It’s also easy to tweak for generating huge volumes of vis, say a covenant wants hundreds of pawns, and it makes sense for that covenant to have a broad selection of vis.
I know of a quirk in the RNG and math applied to determine the Art, but it is small enough to be inconsequential.