In the Rule “Infrastructure”, after “If an Infrastructure’s hit points would ever exceed their default value, they are instead set to their default value. “, add

If a non-Rubble Infrastructure’s hit points would be reduced to or below 0, the Infrastructure becomes Rubble and its Hit Points become 0.

Add a new Infrastructure “Rubble” with a cost of 1 Stone, an Effect of “Migrants in adjacent non-Prison Slots may move into the Rubble.”, 0 Default Hit Points, and Maximum Population 5.

Add a new Infrastructure “Prison” with a cost of “Iron (bar) x 12, Stone (cut) x 6”, an Effect of “Hostile Migrants here cannot take any actions, are removed from any Sieges they’re in, and are not considered Hostile for the purpose of restricting other resources’ movements.”, 250 Default Hit Points, and Maximum Population 5.