Commune is a fifth-circle spell which can be cast by Clerics and Inquisitors, at the cost of ten minutes of time and materials worth between 438𝔾 and 875𝔾², and which enables Iomedae to answer questions with a "yes" or "no" answer at lower intervention cost than a vision would entail. The number of questions available per cast varies, but is reliably at least nine, and is reliably higher for clerics of higher circles.

²See Supplement C for market analysis of materials cost in markets across Avistan.

Unlike most spells, the cost of a Commune is not solely the caster's time and materials (although the opportunity cost of a spell slot and the cost of the components is also not trivial). Instead, each commune question costs Iomedae to answer, and therefore it should be used sparingly. Even though the cost to Iomedae of answering a Commune is lower than giving direct visions, it is still an expenditure of Her divine power and focus, which is not to be wasted unnecessarily. This is why all Commune casts in the Church of Iomedae on Golarion are carried out by individuals who have received training in the subject.

Although the exact economics of divine intervention is not well understood, it is hypothesized that answering a commune question is at least an order of magnitude cheaper than being provided a divine vision of equal information. Prior to the death of Aroden, Iomedae had communicated to her priests that the difference in cost between communes and visions was much lower for her than for Aroden, but that changed for unclear reasons when Aroden died and Iomedae inherited much of his power.

Example I

Imagine you are at a ducal feast with seven Taldane nobility; Duke Black—your host—, Baroness White, Baron Green, Baroness Peacock, Thaumaturgist Plum, Lady Scarlet, and Commander Mustard. Unfortunately, as you convene for the feast, you and the other six guests find Duke Black dead, and clearly murdered. Not only that, but since Duke Black's castle is impregnable, it must be one of the other guests. As you are a Cleric or Inquisitor of Iomedae, you are trusted when you claim innocence, but any of the others are possible suspects. They implore you to use Commune to find the assassin. Commune allows you to ask at least nine questions, as you have the requisite fifth circle to cast it, so you cast it:

Did Baroness White kill Duke Black?

NO

Did Baron Green kill Duke Black?

NO

Did Baroness Peacock kill Duke Black?

NO

Did Thaumaturgist Plum kill Duke Black?

YES

Satisfied, you end the spell, and arrest Thaumaturgist Plum.

Analysis

Before reading on, take a moment to analyze "your" behavior above—in which ways did you efficiently use Iomedae's power and attention? In which ways did you inefficiently use Iomedae's power and attention?

One important way in which the example above demonstrates efficient use of Iomedae's power and attention is that you planned which questions were to be asked in advance, and when you used fewer questions than you had available, you did not improvise questions simply to use them up. Commune questions are not free once the spell has been cast as they are costly for Iomedae to answer. It is always better to waste an available question by not asking it, than to waste Iomedae's power and focus by asking an irrelevant question.

However, the example also demonstrates inefficient use of Iomedae's power and attention. You spent four questions to arrive at the answer, which is luck—it could have taken as many as six (getting YES to the last question) or as few as one (getting YES to the first question). If scenarios like the above were commonplace, on average the above strategy would use three and a half Commune questions. ((1+2+3+4+5+6)/6 = 3.5)

One easy way to improve that number is by never asking the last question; once you have received five NOs, you do not need to ask the last question to know the answer will be YES. This strategy reduces the average number of Commune questions used to three and a third. ((1+2+3+4+5+5)/6 = 3.333)

A more advanced strategy would be to first ask Iomedae "Was Duke Black killed by a man?" If the answer is YES, you know the killer is one of Baron Green, Thaumaturgist Plum, or Commander Mustard. If the answer is NO, you know the killer is one of Baroness White, Baroness Peacock, or Lady Scarlet. After this first question, you still must ask at least one and up to three additional questions, so it changes the possible range of questions from one to six, to two to four. This brings us down to an average number of three Commune questions. ((2+3+4+2+3+4)/6 = 3)

The value of these techniques is at scale. Lastwall routinely spends twenty-eight Commune spells per year, which results in around 250 free questions in that time period. At that scale, the difference between the first and last method above is solving 75 mysteries per year versus being able to solving 83 mysteries. This is the frame in which you should consider this training—it will teach you the ability to solve an additional mystery every 6 weeks through nothing more than the more careful application of existing resources.

Example II

Imagine you are working on the general staff of a foreign king while he prepares his country for war, defending against an invading army sent by a necromancer. The invading army is composed of orcs and led by an undead general. To get to the capital city, M— T—, three layers of defense remain; the ruined city of O—, on the river A—, a low outer wall R— E— surrounding the P— fields, and the city walls themself.

In council, the king argues for sending his son out with a large contingent of the army to O—, where they can hold the river instead of waiting to be besieged. An independent advisor, a local wizard, argues instead for sending a call to arms to a nearby defensive ally, who has pledged support. The king thinks the ally is too far away to help, and would arrive in time merely to see their destruction or victory. Furthermore, a third advisor believes the whole affair is unwinnable, and they should focus on the evacuation of their country west, away from the invading necromancer. This would allow the army to build up over the course of a few years and strike back when ready.

You agree to spend a Commune trying to answer the questions the council disagrees on. After a bit of debate, the council agrees on the following questions:

  1. If we call for aid, will our ally arrive in time to help?
  2. If we send our army to defend O—, will they meaningfully impede the invading army?
  3. Is there any chance of our victory?

However, before you ask Iomedae these questions, you stop and think. Is there a way for you to use fewer than three questions and still get the answers you want?

Analysis

One thing worth noticing is that the questions above, while not having mutually exclusive answers like in the first example, do have relations between the possible answers.

Consider the possibility of the last question being answered NO. In that case, one hardly needs to ask the first two questions. By asking that question first, we can reduce the total number of questions from three to one in the best case and three in the worst case.

Can we improve on this? The answer is yes, but it is not a solution that ought to be immediately obvious. For that, we must learn Rhoffiremn Coding.

Rhoffiremn Coding

This is a method that Knight-Commander Iomedae and her general staff invented during the Shining Crusade to make their Communes with Aroden more efficient. It is named after the seventh circle wizard, Advyat Rhoffiremn, who participated in the invention. Their situation was slightly different—prophecy still existed, and therefore questions less costly, but their wartime footing meant that the opportunity cost of spending a spell slot on a Commune was higher. It is now practiced by the church of Iomedae, as well as certain churches of Abadar and Torag.