Since oops is not awake yet, I thought I'd give you all a taste of what you're up against.
This isn't any formal storyline or anything just what happens between now(Killing Deathwing) and Forum Mafia.
So Deathwing is dead and the world goes back to normal. The Horde and Alliance have land battles here and there, but for the most part everything is finally peaceful. Khadgar recreates Atiesh and brings Medivh back to the mortal world where he studied with young mages in Dalaran, Stormwind, and Shattrath. Adventures have time to adventure the world and discover new places. After the death of Deathwing the Maelstrom closed up and the Naga took control of the Lost Isles. Some adventures took to clearing out the Naga inhabitants until eventually it turned out into an all out war. The Horde marched in slaughtered nearly half of the Naga there and claimed the seas for themselves while the Alliance took the rest of the Eastern Kingdom. The main focus was then shifted to Northrend where they were still dealing with the Scourge clean-up. With the Horde occupying the majority of Azeroth the Alliance had no choice other than to set up treaties with the Horde. Varian Wyrnn thought it was the only way to protect his people...Or should I say his people thought it was the only way they could be protected. Varian then contacted Medivh and asked him if he could get a group of men into Orgrimmar without anyone knowing.
Medivh always remained partial, but thought of it as a challenge. Varian said his mission was to enter Grommash Hold and prove to Garrosh that his defenses at home were weak and that he should return troops back into home allowing the Alliance and Horde to both share the planet. Medivh thought the plan was fine and worked on a spell that turned Varian and some troops into normal mortal orcs. He teleported them outside Orgrimmar and they walked right into Grommosh hold without a second look. Garrosh questioned their motives, but before he could do anything about it Varian slit his throat. The Warchief of the Horde had perished and Varian had his magi teleport thousands of troops into Orgrimmar slaughtering almost everyone. The Horde forces around the world called to arms and slaughtered the Alliance forces around Azeroth. This was the biggest war anyone had ever seen. Medivh couldn't believe what he had done so he vanished for many years.
About 6 after the war started something happened in the Blasted Lands. Fel Orcs came ravaging through destroying all Alliance and Horde outposts. Kil'Jaeden moved through and created Spot Portals for more fel orcs to come through until eventually they took over the southern half of the Eastern Kingdom. The Alliance and Horde were both weakened by the giant war they had been in that they couldn't possibly stop them. More Officers of the Burning Legion moved throughout Azeroth taking control of different locations. Dreadlords ran free and murdered innocent people with hell hounds ravaging through the streets of stormwind. The Burning Legion had been waiting for this opportunity since the "Sunwell Incident". The had their blood elves working around the clock to use the Sunwell to bring back old allies that had since perished. Archimonde was among the first to be revived. With the Burning Legion at it's strongest that it's ever been the Alliance and Horde decided to team up for a final assault on the Sunwell.
The moment they showed up they were faced with Kil'Jaeden, Archimonde, and someone they thought would never show their face on Azeroth again...Sargeras. No mortal survived that battle. The Horde and Alliance were no more. There were only 2 groups of people left...Those with the Burning Legion and those against them. Most people fled to Dalaran where they tried to regain strength. It was under the radar since no Burning Legion armies had been through Northrend yet. Medivh was in hiding trying to forget that he was the one that caused all this to happen. He couldn't think of any way to fix the situation...He could only think of that one day when he caused the catastrophe that was The Great War.
20 years go by and the Burning Legion own Azeroth. Most mortal humans are used as Slaves for the Legion's dirty work and they fear nobody. Sargeras is exactly where he wants to be sitting on a throne in the middle of his fortress that is located just outside The Dark Portal. The story continues shortly after this moment. Kael'thas has been revived, but already parted ways with the Burning Legion in hopes of finding another ally...He searched many places and revived many foes, but none of them seem interested and some threatened to kill him even after he gave them their life back.
You don't need to read all this to enjoy the game, but it's interesting and if you read it all then you'll have more fun with the game I'd hope. Also, I was bored as fuck and just made this story up to piece together events between the two time periods and to rid myself of any continuity errors between the two. Holy buttfuck is this long.