That said, I like my mytharc coherent and reasonably consistent. SPN has two long arc stories - the annual mytharc related to the supernatural, and the one related to Sam and Dean. From my POV as long as the supernatural one serves the character one well I'm happy. And SPN is notable for calling back to earlier events, and to maintaining an emotional continuity rare on TV.
Why am I telling you this? Well you can blame write_light who mentioned something about Ruby, and rather than answer his comment I wrote this! I have tried here to summarise the SPN mytharc. It's not the whole story of SPN obviously - I have just tried to explain the supernatural mytharc over 7 seasons. I got it down to 1700 words!
I have based this all on canon, but I have included my own assumptions and guesstimates. This is certainly not a definitive version - it is very much my POV. Which is where you come in -m what doesn't make sense, what do you disagree with, what questions do you have?
Let me know _ I'd love to hear YOUR interpretation of events.
In the beginning, God created stuff. The first beings he created were the Leviathans, but they tended to want to consume everything else, so God locked them in Purgatory.
God then created the angels. The four archangels Michael, Lucifer, Gabriel and Raphael he considered his sons and they are the only ones who were allowed in his presence. When he created Earth and humanity, he asked the angels to worship these creations. Lucifer objected and there was bitter fighting, as Lucifer refuse to do this. Gabriel tired of this, and fled to Earth where he existed disguised as a demigod – the Trickster.
Lucifer continued to disobey God's commands, and so God ordered Michael to cast Lucifer from Heaven. In order to battle Lucifer, Michael needed to occupy a human vessel – one descended from the first earthly brothers - Cain and Abel.
After being banished, as a gesture of defiance, Lucifer took a human – Lilith – and stripped her of her humanity, so creating the first demon. He then populated his domain – Hell – with the souls of evil people, and those he and his minions convince to sell their souls in exchange for benefits while they are alive. Outraged at Lucifer, God ordered Michael to confine him to a prison, locked with 600 seals – 66 of which need to be broken to open the cage.
At some point God leaves Heaven. Michael takes command of the heavenly host which grows into a militaristic society. They kept watch on Earth, ensuring demon activity was minimised.
In Hell, Lucifer is regarded as a deity, although no demons have ever seen him. In 1972, the demon Azazel manages to contact Lucifer inside his prison. Lucifer lays out a plan for Azazel to effect his release. The plan is that Azael will recruit children descended from Cain and Abel, and prime them with his blood to kickstart the development of psychic powers. The strongest of these will be selected as a champion. Being human they will be able to cross the iron devil's trap surrounding the devil's gate in Wyoming. They will then open the door to Hell releasing demons onto the world. The champion will then lead these demons in breaking the seals and freeing Lucifer. Lucifer will then start the apocalypse and destroy humanity.
As Azazel begins his task, Michael learns of the plan. He cares neither one way or the other about the fate of humanity, but strongly desires to kill Lucifer. So Michael allows Lucifer's plan to escape to progress, at the same time plotting to ensure he will have a strong vessel available for when he fights Lucifer. Part of this involves using cupids to ensure certain bloodlines are bought together and this includes enabling the pairing of Mary Campbell and John Winchester.
Azazel also targets hunter Mary Winchester, killing her parents and John and forcing her to make a deal with him. Ten years later, he enters the nursery of her second son Sam, in order to feed him his blood, but while in the act Mary discovers and tries to stop him and he kills her. Her death drives John Winchester on a search for her killer, and a life on the road with his sons Dean and Sam as a hunter of the supernatural.
Azazel uses his demon minions to keep a close eye on Sam Winchester as he grows up. When Sam stops hunting with his family and goes to Stanford, he has a demon possess his close friend Brady. Azazel needs Sam to return to hunting so as to become the calibre of champion he needs, so he has the demon possessing Brady kill Sam's girlfriend Jess in the same method his mother was murdered.
After Sam joins Dean huting, Azazel's minions, in particular Meg, continue to watch over Sam. When John Winchester finds a gun made by Samuel Colt that will open the Devil's Gate, Azazel acts to retrieve it. Eventually, after causing a car accident which leaves Dean near death, he makes John Winchester trade his soul and the Colt for Dean's life.
Azazel also develops a virus that turns humans into murderous zombies – part of Lucifer's plan for wiping out humanity. He tests it and confirms that Sam Winchester (Lucifer's vessel) is immune to it.
Azazel starts gathering his special children in a deserted town to battle each other and determine the champion. In the end it is soldier Jake Talley who remains after he kills Sam. This leads to Dean making a deal with a crossroads demon - she will resurrect Sam in exchange for Dean's soul in a year's time.
Jake breaks the devils's trap around the gate to Hell, and uses the Colt to open the gate, before Sam kills him. Demons start escaping onto Earth.
In Hell, John Winchester has been tortured - the breaking of the first of the seal on Lucifer's cage occurs "when a righteous man sheds blood in hell". However, he doesn't break, and when the gate opens, he too escapes, and helps Dean kill Azazel.
With Azazel dead, Lucifer needs to make sure his plan stays on track so, unbeknown to any of the other demons, he enlists Ruby as his agent. Ruby is sent to befriend Sam, and to be the one to lead him down a path where he will choose to start using his powers, and consume demons blood thus preparing him both to kill Lilith (which breaks the last seal), and to be a suitable vessel for Lucifer. Lore says "The first Demon will be the last seal", but only Lucifer, Lilith, Ruby and the angel Michael and his commanders know that this means that Lilith must be killed.
As Dean's deal is nearly up, Ruby pushes Sam to use his powers but he refuses. Lilith arrives and banishes Ruby back to hell. The hellhounds come for Dean, and Lilith tries to kill Sam, but finds her powers do not work on him.
Michael orders the angels to rescue Dean – who will be Michael's vessel if he is to fight Lucifer – from Hell. They finally succeed, but not before Dean has spilled blood there, unwittingly breaking the first seal on Lucifer's cage.
Meanwhile Ruby escapes from Hell and convinces a grief stricken Sam to drink her blood in order to develop his powers and avenge Dean by killing Lilith. He continues to work with Ruby even after Castiel rescues Dean.
Some angels who wish Lucifer to return to Heaven rebel, believing that the hierarchy wishes him to remain imprisoned, but they fail. Castiel learns of the angel hierarchy's real plan, but is punished before he can inform Dean.
Finally, the angels reveal to Dean that their plan is for Sam to kill Lilith, so that Lucifer can escape, and Michael can kill him. Before Dean can stop him, Sam kills Lilith and beaks the last seal releasing Lucifer.
Once on Earth, Lucifer finds a temporary host, but starts work to convince Sam to be his vessel. Meanwhile the angels work more coercively to attain Dean's consent to be Michael's vessel.
Lucifer starts the Apocalypse in motion. He enlists the Four Horseman to bring about destruction and chaos including using the "Croatoan" virus.
The archangel Gabriel reveals to the Winchesters that the Horseman's rings can be used to reopen Lucifer's cage. They obtain three of the rings, and finally Death, who does not like being bound to Lucifer, gives Dean his ring and tells him how to use them.
The Winchester's then set their plan in motion – Sam primes himself with demon blood and agrees to be Lucifer's vessel. With Dean having refused to be Michael's vessel, Michael uses Adam Milligan (step-brother to the Wincehsters) and confronts Lucifer. Just before they battle, Sam's connection with Dean helps him regains control of himself and he opens the entrance to the cage and throws himself in, taking Lucifer and Michael with him.
Castiel is resurrected, presumably by the still absent God, having been killed by Lucifer. Raphael has taken control in Heaven and plans to try and release Lucifer and Michael. Castiel tries to oppose him, but is not strong enough. Crowley, the demon in charge of Hell, offers him an alliance. Souls are valuable to both Castiel as power in his fight against Raphael and to Crowley to stabilise his position of power in hell, and Crowley proposes they locate Purgatory, where all the souls of monsters reside.
Castiel agrees. Crowley suggests they use the Winchester's to help. Castiel has already rescued Sam from the cage – although unwittingly without his soul. He refuses to let Dean, who is living a normal surban life, be drawn back into hunting, and so their grandfather Samuel is resurrected, with the promise that Mary will be bought back to life if he helps.
Samuel and Sam embark on hunting down the heads of the monster species, which Crowley interrogates as to the location of Purgatory. Dean is eventually drawn back into hunting, and realises something is wrong with Sam, eventually finding out he is missing his soul. Despite being warned that the torture Sam's soul has undergone by Lucifer and Michael could cause a mental collapse, Dean eventually gets death to restore Sam's soul. Death erects a barrier in Sam's mind to contain the psychic damage.
As Castiel becomes desperate in his attempts to gain power in heaven he finds himself more and more in opposition to the Winchesters. He deceives them as to his true actions and eventually, in his attempt to stop their interference, brings down the wall in Sam's mind.
Castiel finally opens to the door to Puragtory and takes in all the souls from the,
proclaiming himself the new God. He begin skilling all those in heaven who sided with Rapahel, and then takes to slaughtering humans he decides are wrong-doers. However, something else entered case from Purgatory – the Leviathans. They start to take control of him, and he turns to Sam and Dean for help. With Death's assistance they reopen the door to Purgatory and Castiel expels the souls. The Leviathans however remain inside him, and are then loosed on an unsuspecting world.