Hypnos

Hypnos is the minor Olympian God of sleep and has a throne on Olympus made out of clouds. He has three sons: Phobetor, Phantasos, and Morpheus, who are all sleep and dream specialists. His Roman counterpart is Somnus. He has three sons at Camp Half-Blood: Clovis and two others. Hypnos is probably where the word hypnotism got from.

Percy Jackson and the Olympians
[ [The Last Olympian]]                                                                                                                                  In The Last Olympian, Hypnos has a cabin at Camp Half-Blood after he has his own throne on Olympus after the Battle of Manhattan. He gets his own throne after Percy makes all the Olympian gods and goddesses vow to an oath to the River Styx that they should honor 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 Great War such as the Second Titan War that ended with Luke's sacrificial death so that Kronos, Titan Lord of Time and possessor of his body, could not end up destroying Mount Olympus and that Olympus could survive.

The Lost Hero
Annabeth takes Jason Grace, son of Zeus's Roman counterpart, Jupiter, to Hypnos's cabin at Camp Half-Blood when she realizes that Jason's memories are lost from his mind and that Clovis, Hypnos's demigod son, has the solution to why his memories are lost. There, Jason feels that he is starting to fall into sleep and Annabeth tells him that even though Hypnos is the minor Olympian God of Sleep, the inside of his cabin makes everyone fall asleep. They find Clovis asleep and Annabeth tries to get him awake, but he didn't hear her at all. So Annabeth says his name louder, making Clovis jump at the loudness of her voice and he gets up half-awake. Once he hears Annabeth explain Jason's problem of lost momeries, Clovis is instantly awake further and hears the story again﻿.