When you recruit soldiers from the Marid a count of 50 men is added to your Total Soldiers count. You could, possibly need to reach a certain amount of soldiers to attack the Cult, or maybe you choose to divide your soldiers onto various quests (maybe even battle as them, as the hero is not needed for the battle engine) and you must choose which quests you must do.
As Griffin suggests, you may even need a certain amount of soldiers to recruit, or even be recognized by another party. Perhaps even members of the Cult will join you if you have an overwhelming enough amount of soldiers.
There's a lot of potential for this simple counter, and as Craig seems to be fully intended on making this the best RPG ever conceived, it will likely play a large role in several determining factors.