If there is a rule called Round 4, add the following as a step in the Turns atomic action, above setting their own Turn Tracker to -:

Age: Increase their Vivacity by the number of Islands whose Turn Tracker is x

If there is not a rule called Round 4 then carry out the same instruction in the rule called Turns.

Add a new subrule to the rule called Island Characteristics, entitled Vivacity:

Each Island has a Vivacity, which is a non-negative integer tracked in the Great Sea page of the wiki and which defaults to zero.

Any Island with a Vivacity that is below the median amount of Vivacity of all Islands is Sedentary. Sedentary Islands may not achieve victory.