The baku is a dream-eating being in Japanese folklore whose imagery developed from Chinese descriptions of a composite animal. People could invoke the baku after a nightmare and ask it to consume the troubling dream. The same tradition also warns that calling too freely might invite the loss of good dreams or hopes.
A composite creature
Early Japanese images and descriptions combine features associated with animals such as an elephant, rhinoceros, tiger, ox, and bear. The combination differs across sources. It is not simply the living Malayan tapir, although the modern Japanese word baku also names that animal.
Protection during sleep
Baku pictures appeared on pillows, screens, and other objects connected with sleep. A person waking from a nightmare might repeat an appeal for the baku to eat it. These practices made the being protective, but not an all-purpose guardian with one fixed set of powers.
From Chinese lore to modern character
Chinese texts described an animal whose skin or image repelled disease and misfortune, and Japanese tradition reshaped that material around dreams. Edo-period prints, modern illustration, games, and animation changed the appearance again. Each version belongs to a particular period rather than one unaltered ancient myth.