Proposed entity: Alarm Bell
Description: A simple bronze bell mounted on a post, operated with a cord, and usable by any Hearthling in distress.
Materials: 1 Wood Log, 1 Bronze Ingot, 1 Spool of Thread
Placement: Anywhere. May have multiple units.
Function: A Hearthling that spots an enemy will make a run for the nearest alarm bell placed by their settlement (perhaps within a certain range). Upon reaching the bell and interacting with it, the settler will trigger Town Defense Mode, and simultaneously set a Defend Location flag at their feet, summoning active combat units to their aid. When there are no more enemy combatants, the Town Defense Mode is automatically canceled and units return to normal duties, as opposed to manually setting Town Defense Mode, which remains active until it is switched off.
Optional: An Alarm Bell could be preconfigured to interact with a specific combat group, to create a dedicated “Emergency Response Team”.