Hypnos

Hypnos (meaning "sleep") is the minor Olympian god of sleep. He is the son of Nyx and Erebus. His Roman counterpart is Somnus. He has at least three children at Camp Half-Blood, Clovis and two others. Hypnos is where the words 'hypnotism' and 'hypnosis' are derived from. Somnus is where the medical term for sleepwalking; somnambulism is derived from. Hypnos was very cheeky and mischievous as a child, by putting people to sleep at serious moments.

History
Long before the Trojan War, Hera was angry at Heracles and she persuaded Hypnos to make Zeus sleep while she tormented the hero. When Zeus awoke, he was furious. He searched for Hypnos and finally found him hiding in the arms of his mother, Nyx. Zeus overcame his anger and simply warned Hypnos not to try such a trick again and Hypnos went unpunished.

During the Trojan War, Hera wanted to distract Zeus from the battle so she could assist the Akhaians, who seemed to be losing the war. She wanted Hypnos to cast a spell of sleep on Zeus but he refused. At first Hera offered Hypnos a golden throne crafted by Hephaestus, but she was forced to raise the price when Hypnos reminded her of the only time he had dared cast sleep on Zeus.

In preparation for this new deception, Hypnos made Hera swear oaths of her sincerity. He agreed to help her deceive Zeus for the hand of Pasithea, one of the Graces. He turned himself into a bird and, before Zeus could see him, hid in the tops of the trees on Mount Ida. He stayed hidden until Hera had seduced Zeus. When the father of gods was dulled by pleasure and sleep, Hypnos flew to Poseidon and urged him to increase his efforts in helping the Akhaians because Zeus was asleep and unaware of his meddling. Poseidon strode through the ranks of soldiers and urged them on. Finally, his bellowing and screeching roused Zeus from his slumber but, in that short time, the Akhaians had turned the battle back on the Trojans. Hera’s trick had worked. Zeus never found out that Hypnos had betrayed him.

His palace was a dark cave where sun never shines and River Lethe flowed beside it. Although Hypnos wasn't one of the most active gods of that time, he was still famous for his role he played in the story of Endymion and Selene, the former goddess of moon. When Endymion was sentenced eternal sleep by Zeus, he received the power to sleep with his eyes open by Hypnos so he could constantly watch his beloved Selene and because Hypnos himself was in love with the girl.

The Last Olympian
A cabin is built at Camp Half-Blood for Hypnos's children probably after he received his own throne on Olympus when the Battle of Manhattan ended. He gets his own throne after Percy Jackson makes all the Olympian gods and goddesses vow to an oath to the River Styx that they should honor the minor gods and goddesses and claim their demigod children when their children reach the age of thirteen just so that no other unclaimed demigod gets frustrated with the gods and decide to cause another war such as the Second Olympian War that ended with Luke Castellan's sacrificial death so that Kronos, Titan Lord of Time and possessor of his body, could not end up destroying Mount Olympus.

The Lost Hero
Annabeth takes Jason, son of Zeus's Roman counterpart, Jupiter, to Hypnos' cabin at Camp Half-Blood when she realizes that Jason's memories are lost from his mind and that Clovis, Hypnos' demigod son, has the solution as to why his memories are lost. There, Jason feels that he is starting to fall asleep and Annabeth tells him that even though Hypnos is the minor Olympian God of Sleep, even the inside of his cabin makes everyone feel like falling asleep, then Annabeth said, "If you ask me, this place is even more dangerous than the Ares cabin. At least with Ares, you can learn where the land mines are." Annabeth says that Jason almost faded, although he doesn't know if she meant literally. Once Clovis hears Annabeth explain Jason's problem of lost memories, Clovis instantly awakens further and hears the story again. Clovis loves his pillow and hates being away from it so he fell back to his pillow and started snoring again once Annabeth and Jason left his cabin.

Personality
Though not a villain or immoral, Hypnos is far from being the most responsible or honorable god to exist. He has been said to do nothing much but sleep, and didn't play a role in the last Titan War, implying that he is a lazy god (if not the laziest). He also show to be very cowardly in the past, having hid himself in his mother's arms to avoid Zeus' s anger, and when Hera requested his assistance against Zeus yet again, Hypnos only complies when she swore to gave him Pasithea's hand in marriage. He was also described to have used his power immaturely when he was a child, much to the other gods' chagrin.

Appearance
As Hypnos has not appeared yet, his physical description can't be assured. However, he has been said to be the twin brother of Thanatos, so he presumably has the same "teakwood" skin, black hair, golden eyes and dark-purple/blue wings. It's unknown if he has the same physical size and musculature of his brother, though, as Hypnos is said to be quite lazy, but it's been worth to notice that he's a shapeshifter.

Abilities
Despite being a minor god and very lazy, Hypnos seems to be much more powerful than his status and antics leads others to believe he really is, likely because he's a child of Nyx, a protogenos.
 * Standard powers of a god.
 * Flight through levitation or his wings.
 * Hypnokinesis: His signature power that allows to him induce sleep, visions and even manipulate dreams in a very similar way that of his son Morpheus, but to a much more powerful degree, since that while Morpheus took great effort to make Manhattan sleep (and even then only with Hecate's help), Hypnos has been know to use this power in more powerful beings, in which even Zeus (the gods' ruler and one of the Big Three) has proved in two different occasions to be susceptible to Hypnos' power.
 * Shapeshifting: Hypnos can change his appearance into anything that he wants to be, and has been know to turned into a bird in the past.

Somnus
The Roman form of Hypnos is known as Somnus. While Hypnos is the god of sleep and didn't do much in Greek mythology, Clovis (a son of Hypnos) explains that Somnus would kill people that fell asleep at their posts, such as Palinurus; the helmsman of Aeneas, a Trojan hero. Clovis uses his father as an example of how the Roman and Greek gods, while still the same could be very different from each other.

Trivia

 * Somnolence, which is a state of near-sleep or desire for sleep, is named after his Roman counterpart Somnus. Also, somnabulation means sleepwalking (ambulabat means having walked in Latin)
 * Disorders like hypersomnia and insomnia are named after his Roman counterpart Somnus.