Red Oni
Often translated as "ogre" or "demon," Oni are pretty different from both, although either word works. "Oni" were originally conceived as usually-evil spirits, similar to some of the more vicious fairies in western legends, shifting over time into large, brutish ogrelike monsters. They are usually depicted as muscular, red or blue in coloration, horned, and wearing a tiger-skin loincloth, though this varies from oni to oni. Some are said to punish sinners in the afterlife (hence "demon"), although most simply live in the mountains and kidnap or eat people (hence "ogre"). Their signature weapon is a kanabo (iron club), because an actual iron kanabowould be virtually impossible to lift or use, and thus only something with an oni's monstrous strength could wield one. "An oni with an iron club" is a colloquial phrase meaning, "something with an overwhelming advantage." There are also different personalities associated with some different types - red oni are much more savage than blue, for example.
Some trivia: Oni have been in Dungeons & Dragons since the first edition, but were soon name-changed into "ogre Mages" for fear that people wouldn't understand waht an oni was. In 4th edition, however, they reverted to "oni," and gained a little variety, such as taking a few non-oni yokai as creature types, for some odd reason.
Red Oni
Often translated as "ogre" or "demon," Oni are pretty different from both, although either word works. "Oni" were originally conceived as usually-evil spirits, similar to some of the more vicious fairies in western legends, shifting over time into large, brutish ogrelike monsters. They are usually depicted as muscular, red or blue in coloration, horned, and wearing a tiger-skin loincloth, though this varies from oni to oni. Some are said to punish sinners in the afterlife (hence "demon"), although most simply live in the mountains and kidnap or eat people (hence "ogre"). Their signature weapon is a kanabo (iron club), because an actual iron kanabowould be virtually impossible to lift or use, and thus only something with an oni's monstrous strength could wield one. "An oni with an iron club" is a colloquial phrase meaning, "something with an overwhelming advantage." There are also different personalities associated with some different types - red oni are much more savage than blue, for example.
Some trivia: Oni have been in Dungeons & Dragons since the first edition, but were soon name-changed into "ogre Mages" for fear that people wouldn't understand waht an oni was. In 4th edition, however, they reverted to "oni," and gained a little variety, such as taking a few non-oni yokai as creature types, for some odd reason.