Spirit is a broad term referring to creatures including fey (such as telthors), elementals, and incorporeal undead (such as shadows or wraiths).
Many of the spirit shaman abilities are designed to be used against spirits. In addition, the campaign for Mask of the Betrayer greatly involves spirits.
3.5E comparison[]
"Spirit" also is used to refer to any creatures that:
- are in Astral Form or with Astral Bodies
- has the spirit subtype from the Oriental Adventures in the Kara-Tur campaign setting
Neither are currently used in NWN2.