I can also think of a category of beings that refer to themselves in the plural.
The Bible says there was a group of demons that went by the name of legion because they were many And they asked to be addressed as a plurality.
Demons are described as having multiple instances living as multiple inhabitants together in a host. I believe Jesus cast out 7 demons from one woman and the legions living in the madman of ghadera into a herd of pigs who then committed suicide in the Lake janesse or it by drowning.