The Thorn Hedge is a defensive system of Mechanicsburg controlled by Castle Heterodyne. It is comprised of massive thorny vines erupting from the ground around the standard town wall that can be rapidly grown on command to form a nigh-impenetrable barrier. During the climactic moments of the Siege of Mechanicsburg, Castle Heterodyne deploys the Thorn Hedge. Sprouting with such speed and force it can throw heavily armored vehicles, such as a Toothy Tank. Without Castle control, the vines can grow wildly unchecked, as they did when the Take Five Bomb froze the castle in time (though how "frozen" the Castle actually is is [ open to debate] [[Chronology - Volume #|✣ ]].) This feature was originally installed by Agatha's great-great-grandfather, and has caused the hedge to envelop the entire co