I’m not sure how this is connected to the opening of the Gates of of Ahn’Qiraj but there seem to be a world event with the Shade of Eranikus (also seen at the end of the Sunken Temple, one of the most underrated instances) invading Moonglade and sending some “Nightmare Phantasms”.

As seen on the FoH’s thread.

I saved the two main screenshots, the one with the dragon and the one with the invasion. In the case they go down.

I guess it must have something to do with this. (As seen on Pacifist Guild site)