Outsiders

Outsiders
Creatures from the outer planes exist on the material planes as creatures of pure spirit only. They cannot interact with the world except for through hosts, usually living beings willing to allow their body to be co-opted by the spirit of the outsider.

Travel to the outer planes is, according to lore, forbidden for mortals. They are not welcome in those realms and face death or banishment at the hands of the denizens of those places. The planar cosmology is different to the standard cosmology.