Many cultures in their mythology spirits are said to aid people when they have nightmares.  In Japan, these spirits are known as the "Baku”.  The Baku are said to have many different characteristics, but for the most part, they are pleasant creatures who help human beings even if they do have a ferocious appearance.  The chief characteristic of a Baku is that he "eats" bad dreams.  In doing so, nightmares can turn bad into future good fortune.  It was considered good luck to have a Baku spirit around to protect you when you need it, but not necessarily to have one around all the time.  While most of the stories about the Baku are positive, there are also some accounts of the Baku, which might make it an unwelcome visitor! 

The Baku are said to have a very curious appearance, being a composite of several different creatures.  While there is some discrepancy between representations, it is usual to think of Baku as having the head of an elephant (including the tusks) with a lion's mane, the body of a horse or a lion, legs and feet like a tiger, and the tail of a cow.  Other images may have a pig-like appearance, although retaining body parts from other species.  In many cases, it was considered helpful to have an image of a Baku in your bedroom.  Therefore, some people would stitch the Baku's name into pillow cases or sheets as a way to invite him into the room.  In modern times, children are sometimes given a stuffed Baku to sleep with as protection against bad dreams.  In addition to having images of Baku present, people who want their dreams eaten should wake from a nightmare and say "Baku, please devour my dreams!" 

There are many legends and stories surrounding the Baku.  Sometimes, they are said to respond to human entreaty, only going where he is needed and eating those dreams causing the person sleeping distress.  However, another less common depiction of Baku has them existing almost as an infestation in peoples' homes, eating every dream rather than just the bad ones.  People in this situation would thus lose all their dreams, and may even have trouble sleeping at all.  Nevertheless, stories like this are not common.  In fact, it is most common for people to view the Baku as beneficial spirits.