Add the following to the list of Structures:

Volt Tower || Iron, Iron || Sea, Air || 10, 10
Circle || Iron, Stone || Land, Sea, Air || 1, 1, 1

Reduce the Defensive Value of the Stone Wall to 30.

Add the following as a subrule to Stockpiles, called Thought Control:

Once after each Wave is Charged, but before the subsequent Wave is Charged, each Vassal who has at least once Circle in their Structures and whose Damage did not increase as a result of the most recent Wave may recruit an Enemy, which results in their Serfs increasing by 1.