I am running a West Marches style game. I've written about it before. It features several factions of varying size and flavour and I needed a way to represent their actions in the world between sessions without overwhelming myself with homework. Here is the system I've devised:
Goals
The Faction has two goals: Long Term and Short Term. The Long Term Goal is the guiding star of the faction. It is mostly there for flavour and to help determine the much more important Short Term Goal. The Short Term Goal is what the faction is hoping to achieve this week or even this day. It's something that can be done by the faction with its current resources. It's the next step that gets them closer to the Long Term Goal.
Power Level
The Power Level of a faction is a number between 2 and 20 which abstractly represents its capabilities. A power of 20 is a globally dominant superpower. A power of 2 represents a group with the barest level of cohesion. If a group falls below a power of 2 it dissolves.
Testing Power
After every session, roll a d20 for every faction the players have encountered:
Goals
The Faction has two goals: Long Term and Short Term. The Long Term Goal is the guiding star of the faction. It is mostly there for flavour and to help determine the much more important Short Term Goal. The Short Term Goal is what the faction is hoping to achieve this week or even this day. It's something that can be done by the faction with its current resources. It's the next step that gets them closer to the Long Term Goal.
Power Level
The Power Level of a faction is a number between 2 and 20 which abstractly represents its capabilities. A power of 20 is a globally dominant superpower. A power of 2 represents a group with the barest level of cohesion. If a group falls below a power of 2 it dissolves.
Testing Power
After every session, roll a d20 for every faction the players have encountered:
- If you roll on or above the faction's Power Level nothing changes.
- If you roll below its Power Level the faction accomplishes their goal and increases their Power Level by 1.
- If you roll a 20 the faction suffers a setback and decreases their Power Level by 1.
- If you roll a 1 the faction accomplishes their goal, increases their Power Level by 1, and can choose to knock another faction down by 1 (decide how this was done within the fiction).
This hasn't come up yet in my game but if the players directly impact a faction's Power Level by helping (clearing out a new outpost, securing supplies, etc) or hindering (destroying a resource, humiliating the leader, etc) during a session, I wouldn't bother rolling.
What does Power Level determine anyway?
The Power Level can be used in a number of ways. Use it to determine the number of members you might encounter in the world on a mission (a Level 2 faction can only field 2 members at a time). The Faction might have named NPC agents whose HD adds up to its Level (a Level 10 faction may have an HD 4 magic user and an HD 6 assassin on their payroll). If you're running a hexcrawl you could use it to determine how many hexes they control. You could say the faction has 100 x Level coins in their slush fund.
What do the players experience?
Tying this stuff into the game play experience is key or else it is rendered completely meaningless. As factions grow the people of the world should take notice. NPCs might remark on how the Bent Nail has been hiring up all the fighting-age youths in the region, or how the selection at the market has improved since the cart bridge was repaired by the local do-gooder faction. When the factions pick Short Term goals, pick ones that are dramatic and will result in dramatic revelations in the short or medium term.
Worth noting that as a faction's Power Level increases, it becomes more likely to increase next time. This can cause a cascading effect, so make sure you communicate this to your players either in the narrative or out of it. A faction might reach out to the players for help in taking a breakaway faction down a peg or two.