I have a player who would like his character to begin developing a network of people in the towns they visit. For lack of a better phrase, and because it seems that would be the most likely mechanic to exist out there, it would be a "spy" network, although the members wouldn't necessarily be spies.
This network would kind of take the place of building a stronghold or similar domain, so I've been looking at those rules in D&D, but they don't seem to fit what we have in mind.
What we're looking for is a way to at least partially abstract the process of finding likely members and track the "health" of the network. Some good tables for generating events that affect the network and/or information they turn up and pass around would be an added bonus.
We're playing D&D 4e using the Legend & Labyrinths house rules, but the mechanic doesn't necessarily have to be from a D&D system.
Best Answer
Use Reign to model competing spy networks. Use Ars Magica to play Spy v. Spy with your PCs being spymasters
To amplify Gomad's point, Both Reign and Ars Magica have excellent spy-network subsystems which I've used.
The Reign company rules do not require sovereign rule over a territory, as multiple companies can spatially co-exist. Therefore, they are perfect for modelling competing spy networks and providing a largely abstracted but manipulatable way of gaining information, sowing disinformation, and tying the actions of the PCs into the consequences of spy success or failure.
The Ars Magica agent rules (found in
Houses of Hermes: Societiesare far more specific and crunchy, though easily adaptable to any given system. They provide for hierarchies of agents, their advancement, and all standard espionage actions. They are far better than Reign's rules for spending quite a lot of time exploring the spy game, but thereby take more time and effort to resolve.Amusingly, the systems can even be combined without too much effort, although the complete combination would be the answer to another question. (hint, hint.)