Fortune telling is one of the hardest things for a GM to work into a game. When the prognosticator lays out those cards, or gazes into that crystal ball, things tend to go south fast. When it's the GM laying out the future, the tendency is to get locked into a choo choo experience, and when its the PC peering into the future, it just usually ends up making no sense at all.
So here I am, putting astrology into OHMAS with the Savant path - so what's up with that?
When I researched the people on which I based the Savant, one thing all had in common was Astrology, so if I wanted to remain true to my source, I needed to somehow integrate Astrology into the game in a way that would allow the player character the chance to make meaningful predictions, while at the same time not locking things in to the point of pre-destining the game.
I went back and really looked at Astrology in the real world - how is it supposed to work? How has belief in astrology lasted since antiquity? Maybe if I based the game mechanic on the real thing, it would solve the problems which seemed inherent in game-based fortune telling.
The key seemed to lie in the attitude towards what the stars actually were presumed to do. The planets influenced events. They did not dictate events. Futhermore, each planet had a sphere of interest - Venus ruled romance, but had no power over fighting. Jupiter presided over fortune, not reason. So I had to create an abstracted game sub-system where the planets could influence things in their sector, but allow the GMs and players to play without pre-determined results forcing things into any given path.
What I came up with was a system of random bonuses, good for the day, and good all day. If you approach a problem in this sphere in this manner, then you have a bonus:
Roll Luna Mercury Venus Mars Jupiter Saturn
rules Emotion Reason Romance Conflict Fortune Order
1-2 Fear Deliberation Flirtation Trickery Secrecy Boundaries
3-4 Hesitance Inspiration Subversion Might Timing Laws
5-6 Horror Analysis Sex Indirect Boldness Customs
7-8 Anger Deduction Seduction Flanking Lavishness Families
9-10 Doubt Mystification Titillation Position Prudence Organizations
11-12 Affection Appreciation Fascination Intimidation Investment Channels
13-14 Lust Deceit Ingratiation Brutality Trust Ethics
15-16 Confidence Misdirection Sympathy Glory Miserliness Morals
17-18 Longing Compromise Intrigue Caution Distrust Patterns
19-20 Joy Persuasion Beauty Opportunity Openness Connections
So, the Savant decides to see what the stars have in store for Conflict, Romance, and Order, becasue those are the sphere she judges are most important. For Conflict, she rolls a 12, indicating Intimidation is favored. In any situation of conflict, attempts relying on intimidation gain an extra die. For Romance, she rolls a 7 for seduction. In any action concerning romance, the PCs can gain a bonus dice if they are trying seduction. For Order, she rolls a 2, for a result of Boundaries. In situations where order is important, somehow involving boundaries will gain the PCs a bonus die. In upcoming situations, the PCs will tend to use these methods because they are favored.
Simultaneously, the GM reads the prophecy backwards to put in opportunities for those methods to work. How these factors are involved can involve creative interpretation, but they give a seed for the upcoming situation. Don't worry about the PCs. they will supply their own creative interpretations. The NPCs also can use these bonuses if they know of them. These influences are literally in the air, and anyone can use them. The PCs have a relevant prophecy, and the GM has a situation seed without railroading.