The Day of the Departed is a sacred holiday celebrated by the people of Ninjago. Once every year, the citizens light lanterns to commemorate their fallen ancestors and friends, while also spending time with their families.
Following the Sky Pirate conflict, Ninjago celebrated the holiday once again, with the Ninja spreading out across the land of Ninjago to remember their ancestors. Zane remembers Dr. Julien at Birchwood Forest, Kai and Nya remember Ray and Maya at their blacksmith shop, Lloyd and Misako remember Garmadon at the Corridor of Elders, and Wu remembers his father at the Monastery of Spinjitzu, while Jay spends time with his parents at their junkyard.
In the meantime, Cole goes to Master Yang's Haunted Temple to settle his debt with the ghostly master. However, a sinister plot by Yang leads Cole to free the spirits of the Ninjas' old enemies from the Departed Realm, including Samukai, Kozu, Cryptor, Chen and Morro, all of whom possess statues at the Ninjago Museum of History. Seeking revenge, the revived villains spread throughout Ninjago to confront their adversaries.
- The holiday seems to be a combination of several different traditions from many different cultures, including Halloween, Memorial Day, Día de los Muertos (The Day of the Dead), and Chinese and Japanese Lantern Festivals; it involves costumes, candy, celebrating and honoring the dead, and lighting lanterns for one's ancestors. In particular, it seems to draw inspiration from the Japanese festival of Obon, a similar holiday to Día de los Muertos in which the spirits of one's ancestors are honored.
- The characters release Lanterns into the air to honor spirits, of the deceased, similar to Bon Festivals in Japan.
- In the Holiday, spirits come back from the Departed realm and enter statues of themselves, this based off how spirits would supposable visit household alters during Bon Festivals.
- People also settle their debts on this day.