A being that is a level-zero god.
Immortals have somehow achieved the first level of god-hood by being able to transcend the limitations of a corporeal form.
Once they have achieved this status they must start to acquire followers if they wish to progress in power as a deity. This is not always possible because what often happens is that they have to take followers from another god to do so. ]
Many immortals become the emissary of a patron god. Offering their abilty to directly interact with the material world in exchange for power, protection or favor.