While there were a few other options for titling this post, this cliché truly feels appropriate at this moment. Kael'thas is without a doubt the most difficult raid boss we've faced as a guild. He is the gateway to Hyjal and the Black Temple, and that gate is not easily traversed.
The fight begins simply enough with the slow procession of 4 advisors that are killed sequentially. Each advisor has unique abilities, but all very managable. This phase is followed by the appearance of 7 legendary weapons which must be defeated and equipped even. Didn't you always want your very own legendary? After the weapons demise, is when the fight starts to get serious. Kael'thas simultaneously raises all four of his charming advisors from the dead to wreak havoc on the raid. Finally, after defeating all the minions of Kael'thas you get to fight the man himself. His fireballs and pyroblasts are no joke at all, not to mention the baby phoenixes that he summons. He seemed just a little upset that we killed his "burd." However, if you have survived this long with all of your raid alive, then you are very close to a kill.
All in all, this fight is brutally unforgiving, much more so than Lady Vashj. While there are significant techinical complexities to the fight, remaining focused through the attempts is actually a significant challenge to the fight as well. If at any point players lose awareness, even the trivial first phase can result in a player death, effectively ending the attempt. This is the most frustrating aspect of the fight, and at one point last night I would not have cared if a GM swooped down from the sky on a netherdrake and one-shot Kael'thas; I just wanted him to die. In the end though, the fight feels epic and killing Kael'thas feels like a true accomplishment. I would like to take a moment to thank everyone that showed up night after night to learn this encounter and did not give up. I hope that seeing the emblem of Kael'thas burning in Shattrath City was as rewarding for you as it was for me.