Dionysus is the god of wine, and the son of Semele and Zeus. He is also known as Mr. D, the Camp Half-Blood camp director.
Dionysus is not only the God of Wine, but also the God of ritual madness/ecstasy, as well as the 'cult of souls' because of he looked over the communication between the living and the dead.
Greek Mythology
Dionysus was often called the 'twice born' because of some of the myths around his birth. The most common is that his mother was a mortal woman named Semele, who was a daughter of the King of Thebes, and his father was Zeus.
As with most of Zeus' acts of infidelity, Hera became jealous when she found out that Semele was pregnant with Zeus' child. She disguised herself as a nurse (or old crone in some stories) and made Semele begin to doubt that it was truly Zeus. While in disguise, Hera convinced Semele to ask Zeus to reveal his true form, and to make sure that he would do it, to swear on the River Styx, which is sacred to the Greek Gods, and was an unbreakable oath.
Zeus tried to get around the promise, but in the end swore on the River, and Semele asked to see his true form. Unable to go back on the promise, he did so, and she was burned to ash.
Zeus managed to save the infant, sewing him into his thigh until he was born a few months later as a full grown baby on Mount Pramnos in Ikaria. This is how he became a true God, instead of only half, although sometimes later in life he is granted divinity after sparing some of those who had kidnapped him.
In his early life Zeus sent Dionysus off with Hermes. Again here, there are two versions of the story. In one version, Hermes took Dionysus to King Athamas and his wife Ino, who was Dionysus' Aunt. Hermes had them raise Dionysus as a girl to hide him from Hera's scorn. The second story is that the boy was taken to the rain nymphs of Nysa. They raised him through infancy and childhood. And in reward for their care, Zeus placed them as the Hyades in the stars. The main idea was to hide the child from Hera's continuing wrath.
When he grew up, he discovered the vine, and extracting the juice. He was struck with madness by Hera at this point, and ended up wandering various parts of the world. Rhea cured him, and taught him her religious rites, and he wandered through Asia teaching about cultivating the vine.
He was very handsome as a young man. He was disguised as a mortal on the seashore once, and a few sailors spotted him.They thought he was a prince, and tried to kidnap him and hold him for ransom or to sell into slavery. They tried to tie him up, but no ropes would hold him. Some ideas are that the material they were made of then was similar to the vines, and would refuse to hold him. At this point Dionysus turned into a lion and let a bear loose on board. It killed those it came in contact with, and those who jumped off the ship were turned into dolphins as an act of mercy. The only one to survive was the helmsman Acoetes, who had recognized him as a God, and tried to stop his comrades from the beginning.
A second story was very similar, except that he had hired a pirate ship to get him from Ikaria to Naxos. The pirates sailed to Asia instead once he was aboard, wanting to sell him as a slave. Dionysus turned the mast and oars into snakes and then filled the boat with ivy (a plant sacred to the god) as well as the sound of flutes to drive the sailors mad, who leaped into the water, and were then turned into dolphins.
When he grew up, Dionysus rescued his mother from Hades, and she became a goddess on Mount Olympus, with the new name Thyone, presiding over the frenzy inspired by her son Dionysus.
When Dionysus was invited late to the Mount Olympus, it was Hestia who graciously offered him her golden chair to prevent any conflict or embarrassment. Hestia was a goddess known for her warmth and kindness.
When Theseus abandoned Ariadne sleeping on Naxos, Dionysus found and married her. When she died, he went to the Underworld and rescued her, taking her up to Mount Olympus, where he made her immortal.
Camp Half-Blood
After chasing after an off-limits wood nymph, Zeus punished him by putting him in charge of Camp Half-Blood for 100 years. During this time, he is not allowed to drink wine or grow wine grapes. He is rather chubby, as are his children. Dionysus is known to be rather sarcastic and rude. He enjoys calling people by incorrect names, especially Percy Jackson who he often calls "Peter Johnson". He sometimes does this with campers who have been for long at camp for a long time, such as Annabeth Chase who he calls "Anniebell".
During the final book he is one of the God's fighting Typhon although he is knocked out.He is later seen at the end when he comments that Percy might not be so bad after all[He also uses his actual name,which is Percy then points out and Dionysus denies].
Children
Film
In the upcoming film, The Lightning Thief, Dionysus will be played by Luke Camilleri.