Time - every 300 seconds of game time
Set point = center of region
Unit - Create x of y at point
Custom script : call RemoveLocation(udg_point)
Custom script : set bj_wantDestroyGroup = true
set unit = random unit from units matching matching unit is alive and matching unit is of type town hall
Set point = position of unit
Unit group - order last created unit group to attack move to point
Custom script : call RemoveLocation(udg_point)