For the quest in The Elder Scrolls V: Skyrim, see Ancestral Worship. 

The Dunmer believe that the spirits of the dead live on in Nirn. They can know and affect the future, and can speak with other spirits, and work great magic, so the Dunmer honor and give gifts to them, and ask them for aid and protection. Strong spirits of warriors and wise women preserve the honor and wisdom of the race. The worst spirits are evil and harmful called ghosts, devils, and demons. The oldest of the great ancestor spirits are the Daedra. They are powerful, but dangerous, and hard to understand.