So I was just running around levelling weapon skill on my new Shaman and happened upon the Lich King just hanging out in Scourgeholme. I landed in front of him and the Deathspeaker mob in front of him aggro'd on me, which then turned the Lich King aggressive and I could attack him! Well, I thought, I wonder if you can kill him and if you do does he drop loot? So I hopped on my Fury and he does a bit too much damage to self heal through.
He has 27.9M HP and has no mechanics, I was tanking him solo for a while on my paladin before anyone showed up. Just a low geared rogue and myself (a couple of others appeared but left after a few mins when they saw how slow it was) spent about 45-50 mins killing him and we got a nice surprise!
He drops nothing and just T-Poses to flex on you.
Not sure if anyone found this bug before but I thought it was pretty funny.