Halloween is a holiday event taking place in November each year. The history of the Kaelicious social group begins with the Halloween-event named "The Mad King's Realm" in 2012. In 2013 there was arranged no Halloween-event in the group due to Bernkastel, who was maintainer of Kaelicious at that time, having distanced the group from the Kaelicious universe until December 2013.

In both universes, the Halloween holiday is closely related to the demon civilization of Hell, which coronates their king and leader, the Idol of Halloween, before the Hand of the Fire God the first of November, usually after a long October month of civil wars over the honor of bearing that title. During Halloween the new Idol is then encouraged to lead an attack upon the human cities and villages of Easterland, called trick-or-treating, since the humans are then allowed to make a choise. Treat - handing over all of their riches, and be left in peace, or trick - if the demons meet any resistance or defensive forces in Easterland, the punishment will be destruction and no mercy.

Due to the first Kaelicious-event being based on the Halloween-holiday, the first novel in the Hollideus Project is going to be based on that event as well, with the title "Hollideus I: The Horrors of Halloween".