Liminal deity

A liminal deity is a god or goddess in mythology who presides over thresholds, gates, or doorways; "a crosser of boundaries". Special types include dying-and-rising deities, various agricultural deities, and those who descend into the underworld: crossing the threshold between life and death representing the most fundamental of all boundaries.
Vegetation deities in particular mimic the annual dying and returning of plant life, making them seasonally cyclical liminal deities. In contrast, the one-time ordeal typical of the dying-and-rising myth, or legends of those who return from a descent to the underworld, represent a more narrow scope of liminal deities.
Etymology.
The word "liminal", first attested to in English in 1884, comes from the Latin word "limen", meaning "threshold". "Liminality" is a term given currency in twentieth century anthropology by Victor Turner of the University of Chicago.