If you need a little refresh on the lore, the content takes place against this backdrop:
“Fresh from his defeat in Outland, Kael'thas Sunstrider returned to the blood elf city of Silvermoon. Rather than lead his people to glory as he had promised, the disgraced prince betrayed them. Kael'thas plots to use the legendary Sunwell, source of the blood elves' magical power, to summon the demon lord Kil'jaeden into Azeroth. It is up to you to stop him.”
It’s always up to you to stop the next plan, so you should already have plenty of experience doing so. This time you’ll be able to complete a series of daily quests and gain reputation with the Shattered Sun Offensive, which has formed to counter Kael'thas. You’ll help them with their preparations and plan your next moves. Over time, there will be more reinforcements, goods and services available, and eventually allies of your own to recruit. You'll also get access to Badge of Justice vendors, where you can obtain epic gear and gems.
The Sunwell Plateau raid is, of course, one of the central features of this update. The 25-player raid will test you and your team with six bosses, including Kil'jaeden, of the Burning Legion, who Kael’thas has succeeded in summoning to Azeroth. Level 70 raid will not require attunement to enter and it will debut with all of its bosses included from the start.
So if you’ve been looking for some new challenges for Classic, this update will be live soon, along with the new Burning Crusade Classic season. Season 4 rewards will include the Brutal Gladiator title, the Brutal Nether Drake mount, and Gladiator and Brutal Gladiator gear. Those gear items will require a certain rating before you can buy them, as in the original release.