Spongiform

The Spongiform is a fungi found growing on the trunk and branches of the Blighted Tree. Those who consume it fall into a docile state and lose all semblance of their usual personality. It makes a prominent appearance in Wildwood Imperium and was harvested by the Synod and fed to new Caliphs in order to take over all of Wildwood.

History
Presumedly, the Spongiform has been present for as long as the Blighted Tree has, along with its devout Synod and Caliphs, who use it to recruit new members. The practice of feeding it to assume control over others was employed long before the events of the book, before the Bicycle Coup, even when the Synod had significantly less control and members than it amassed during ''Wildwood Imperium. ''

Nature
Inspired by real life transmissible Spongiform encephalopathies, the Spongiform is a parasitic, moss-like fungi that grows on the trunk of the Blighted Tree. It's brownish green in color, and at times, glows a "phosphorescent green," which suggests that contians woods magic from the Blighted Tree itself. It has an "acrid, bitter flavor," but those eager to consume it don't seem to mind the taste.

Once consumed, the Spongiform takes residence in the victim's nostils, eye sockets, and skull, and continues growing. In Seamus's case, the Spongiform formed a small seed, from which grew an expansive root system that resided within his nasal cavities and skull. Like all other plants, Prue was able to communicate with the Spongiform and command it to exit Seamus and the other infected people she helps.

To Prue, the Spongiform emits a ticking sound that grows louder the closer she is to great quantities of the Spongiform or infected individuals. It's loudest when she's near the Blighted Tree, the main and only known source of Spongiform.

Appearances
The Spongiform made a prominent appearance throughout all of Wildwood Imperium. It first appears in chapter 13, "A Meeting at the Tree."

The Wildwood Bandits
The Wildwood Bandits, including the Bandit King himiself, fell under the influence of the Spongiform thanks to Seamus. Sometime after the events of the first book (likely not soon after Prue is taken to the hideout in Under Wildwood), Seamus had gone to South Wood for meeting with the Synod to discuss reparations in the wake of the Battle of the Plinth. From there, the Synod fed him the Spongiform and sent him back to the bandits' hideout with food rations, which contained Spongiform. He fed it to the other bandits and its influence spread throughout the camp, until they all left their hideout in the Long Gap and moved to South Wood, where the Synod and Blighted Tree were stationed.

Curtis, who had left the hideout with Prue for Iphigenia's funeral, did not fall victim to the Spongiform, and, along with Septimus, was the last Wildwood Bandit for many months, until Prue cures the other infected bandits in part 3 of Wildwood Imperium.

The Population of South Wood
Prior to the Bicycle Coup, a small number of South Wood citizens were part of the Synod and had ingested the Spongiform. After Lars Svik was overthrown, the Synod were able to recruit new members and spread the infection without issue. When Prue is summoned to the Blighted Tree in Wildwood Imperium, Spokes and Svikists alike were lined up to consume the Spongiform.

By part 3 of the book, almost the entire population of South Wood, including Kendra, had been indicted into the Synod and eaten the Spongiform. Zita's father had just become a new member and would also have eaten it sometime in the near future.

Trivia

 * In real life, transmissible spongiform encephalopathies in humans cause Creutzfeldt–Jakob disease, an invaribly fatal degenrative brain disorder. In animals, it causes bovine spongiform encephalopathy (better known as mad cow's disease) in cattle and sheep, and causes chronic wasting disease in deer and elk. Considering that the Spongiform in the Wildwood Chronicles series grows into a significant mass and takes residence in the skull, it would be reasonable to assume that in real life, those infected would suffer permanent brain damage and death, even after it was removed.