Eternal Life Spell (1)
In modern Western magical traditions, only Palo Mayombe acknowledges the use of human bones. This was once not unusual however. Despite all the Halloween skeletal imagery, few today have actually seen exposed, bare human bones. Once upon a time this was not so unusual (and the practices still survives amongst some isolated traditions). Bodies were disinterred for various reasons having nothing to do with vandalism.
Certain traditions disinter ancestors periodically to invite them to rituals and celebrations, returning them to the grave at the conclusion
Other traditions retain ancestral bones to honor and communicate with them
Particularly in areas where land is scarce, bodies may only remain underground as long as flesh remains. Bones are permanently moved to catacombs or ossuaries
Bones are also disinterred so that magical rituals can take place to preserve the deceased’s soul for eternity or to activate the reincarnation process.
Paint human bones red to magically provide the deceased with eternal life, of one sort or another. Menstrual blood was the most ancient activation material; however red ochre has also been used since prehistoric times.
(from The Element Encyclopedia of 5,000 Spells by Judika Illes)