Oriental Adventures said:Spirit creatures include some fey and elementals (nature spirits), outsiders (celestial spirits), undead (ghosts and ancestors), and even dragons. Spirit creatures are not necessarily incorporeal, despite their name--in the worlds of Oriental Adventures, some spirits are as much flesh and bone as humans are. The only game effect of the spirit subtype is that spirit creatures are all affected by spells such as commune with greater spirit, invisibility to spirits, and protection from spirits.