Earthbound evils

While demons typically arise within the lower planes (and are largely trapped there), some people are so evil that their souls may become demons without ever leaving the material plane. Likewise, some terrestrial spirits may become so corrupt that they are twisted into demons. Some may build fleshy bodies for themselves or reincarnate within family lineages. These earthbound evils are commonly known by names like div, oni, rakshasa, and sahkil depending on the local culture. Pathfinder introduces all of these as new races of demons, but I prefer not to split hairs. The rakshasa and ogre mage in the MM are examples of such demons, but they come in many more varieties (see the PF bestiaries for ideas and then build them using the DMG guidelines).