Dream in Myths and Legends

Hypnos/Somnus (Greek/Roman)
A son of Night and Darkness, a brother of Death, Hypnos is a calm God, who likes humans, helps them and owns half of their life.
Phobetor, Morpheus and Phantasos (probably Ovidian inventions)
Sons of Somnus, they appear in dreams in different forms:
Phobetor as animals (he is also portrayed as a bringer of nightmares), Morpheus as human (and a dream messager) and Phantasos as objects.
Baku (Japanese)
A deity who devours dreams and nightmares. He is a chimaera, mix of different animals. He is a shy deity, who, in one of the versions, comes to children to eat their bad dreams and let them sleep peacefully.
The Nightmare, by Henry Fuseli, 1781
Mare (German, Norse, Slavic)
A creature, that sits on your chest while you sleep and brings nightmares. It was a creature that explained dream paralysis.
Worry Dolls (Guatemala)
Children take a doll and tell it all of their worries before going to sleep, while they sleep, Doll takes care of those worries.
Past Future Present
Aboriginal people of Australia believe that in dreams Past, Present and Future coexist.
Dream Catchers
Asibikaashi, the Spider Woman, a goddess of a Native American tribe Ojibwe, protects her people from nightmares through these dreamcatchers.
He sprinkles sand in the eyes of sleeping kids, so they dream.
Multiple Aspects
In Norse mythology dream served several purposes: they could foretell future, help to contact other beings or to bring hidden knowledge.