One of the major lessons that Moundshroud imparts to the boys is humanity’s need to recognize mortality. This is closely tied in with the spirit of Halloween itself. As Moundhshroud points out, Halloween evolved out of customs related to death and burial, allowing various cultures to deal with this fact of existence, which is fundamental not only to human life but to nature broadly; Moundshroud notes, for instance, the seasonal dying of plants in his discussion of autumn festivals. Recognizing mortality also implies the need to remember and honor the dead, as Tom learns from the Mexican celebrations and as the funerary practices of ancient Egypt suggest.

Although emphasized throughout the book (especially through the use of bones and other symbols of death), this theme culminates when Moundshroud encourages the boys to sacrifice a year of each of their lives to save Pipkin—an act that entails accepting death in an unusually immediate way. By the time Moundshroud communicates to Tom that he will come to gather him at the end of his life, Tom is at peace with his mortality. This speaks to the book’s contention that awareness of mortality need not result in a gloomy or morbid frame of mind.