A Grine is a spirit conforming to a particular description, which is found both in the folklore of Morocco and in modern literature.
In Moroccan myth, each time a human is born in our world, a djinn called a Grine is born in another, adjacent world. The actions of the human inevitably influence the actions of the Grine, whereas the actions of the Grine inevitably influence those of the human.
In Contemporary Literature
Wayne Thomas Batson's The Door Within Trilogy features a race of humanoids called Glimpses, who dwell in a world adjacent to ours. Each Glimpse corresponds in action, appearance, character, birthdate, and time of death to a human that lives in our world. If a human travels to the Realm of the Glimpses, the corresponding Glimpse will disappear for as long as the human remains. Glimpses have white skin and eyes that change color according to their political alliance.
The Alosha series written by Christopher Pike (author) describes all "elementals"– elves, dwarfs, leprechauns, faeries, trolls, dragons, etc.– as similar to Grines, in that when an elemental dies, a human with similar character traits is born, whereas when the human dies, the elemental is either reborn or revived, depending on the condition of its previous body. The bodies are, as a rule, preserved by the angelic "ice maidens". The soul travels back and forth between the human and the spirit world, ultimately to evolve into an ice maiden and thence into a God. This description connects Western ideas of spirits with the Indian idea of the Gandharvas and Apsaras who are born on Earth as animals or demons as a result of their errors, as well as with the idea of a "spirit world" to which the dead travel for their continued existence