A Brief History of Amber
As best you can tell, Amber has existed for thousands and thousands of years. And during most of that time, Oberon has been king. There is no information how Amber was formed or anything. As far as history books are concerned, Amber has always been.
Life spans are much longer in Amber than you are used to. The general citizens can expect to live several centuries before dying of old age. The royal family can apparently live thousands of years. How long they can live is unknown. No member of the royal family has ever died of old age.
In addition to their long lives, the royalty of Amber also possess powers that the general citizens do not comprehend: instant travel and communication, ability to travel between worlds, superhuman strength and endurance. This is on top of the powers that the general citizens can comprehend, like common sorcery.
About seven years ago, things started to go to hell. Oberon disappeared. He was gone for about a year before his sons started quarreling over the throne. Bleys, Fiona and Brand represented one faction, Eric, Julian, Caine and Gérard another faction. Eric’s cabal had home court advantage, since they already controlled all of the military, and Eric was named regent. Deirdre was made a prisoner of the Crown. It was all pretty ugly.
Things were tense for a few months. Caine ended up getting badly wounded after they had captured Brand. Then Corwin appeared. He and Random drove a car up into Arden, kidnapped Julian for a bit, rescued Deirdre, and gained asylum in Rebma. Then Corwin comes back again leading armies against Amber with Bleys. The attack was a near thing, but Corwin and Bleys were herded to a place were Eric’s forces were able to slowly crush their Shadow army. Bleys fell to his death from the stairs leading up the face of Kolvir, Corwin was captured alive. He lived long enough to see Eric’s coronation and he was subsequently blinded and tossed in the dungeons for the next four years.
Over the next few years as the Valley of Garnath darkened, strange things attack Amber through there. It starts out with the occasional manticore or demonic thing. After a few years, Amber was fighting inhuman seeming albinos riding on the backs of wyverns. A sinister black road ran through Garnath, bringing in enemy forces from somewhere in Shadow. The general populace believed this was all due to some curse Corwin placed on the place.
In the last big battle, Corwin showed up with troops wielding machine guns that actually work in Amber, and he helped fight off the attack. Eric died from wounds sustained during the fighting. And Corwin… took charge of the place.
After that, the fighting stopped and the tension resumed. Many of the events prior to your arrival in Amber are jumbled and confusing, since most of the people privy to these things are gone off to fight in the last big battle. Caine was murdered, Brand returned to Amber from some sort of imprisonment and almost murdered. Then it comes out that Brand was responsible for the things attacking Amber, and there was a lot of work to try and stop him from causing more trouble.
Then Oberon showed up out of the blue. He took control of things, troops had been marshalling, you were brought into Amber, and then everyone left. Since the big storm on your first day in Amber, Oberon has not reappeared.