[Mod request] Prisoner Exchange Program

[AngleWyrm]

Sometimes invaders will take a captive, and then later on offer their return in exchange for silver.

• If I have one of their faction members prisoner, might be worth an exchange price maybe with a silver offset for difference in value
• If a costing system can be worked out, then offering prisoners back to their factions could also be a form of direct exchange for silver when no captive is available for exchange