Hypnos: the god of sleep who once knocked out Zeus himself

Short answer: Hypnos is the Greek god of sleep, son of Night and twin brother of Thanatos, death itself. The Greeks made sleep and death twins on purpose: one takes you for a night, the other forever. And unlike almost everyone in the pantheon, Hypnos has beaten Zeus. Twice.

The god even Zeus couldn't resist

During the Trojan War, Hera needed Zeus distracted so the sea god could help the Greeks. She recruited Hypnos, who had done it once before and had been chased across the sky by a furious Zeus for it. He only agreed the second time after negotiating a wedding: one of the Graces as his bride. Then he perched in a pine tree disguised as a bird, and the king of gods, the wielder of thunder, simply fell asleep. Every power in myth has a counter; sleep has none.

His strange family

Relative	Domain
Nyx, his mother	The Night: even Zeus fears her
Thanatos, his twin	Peaceful death; they carry fallen heroes together
Morpheus, his son	Dreams: he shapes the people you see while sleeping
The Oneiroi, his sons	The tribe of dreams, true ones and false ones

Homer says the twins once carried the hero Sarpedon's body home from the battlefield together: sleep and death as pallbearers, one on each side.

Quick questions

What does Hypnos look like?

A calm winged youth, sometimes with wings on his temples, carrying a poppy stem and a horn of dripping sleep. He lives in a silent cave in the underworld where the river Lethe, forgetfulness, flows by his bed. No door, so no creaking hinges.

Is Hypnos evil?

The opposite: Homer calls him "the sweetest of the gods." The Greeks saw sleep as a nightly mercy, the only one that visits kings and enslaved people alike.

Hypnos vs Morpheus: who does what?

Hypnos IS sleep, the state itself. His son Morpheus makes the dreams inside it, appearing in them shaped as any human. The drug morphine is named for the son; hypnosis, for the father.

For his family in action, go to his twin. In MythologyNow, Thanatos gets chained by a king who refuses to die, and chapter 1 of Sisyphus plays in full on this site. The ferryman Charon, another child of Night, is worth meeting too. Good headphones, lights off.