There are 4 Dragons of nightmare: Emeriss,Ysondre,Taerar and Lethron and they can be found in Ashenvale,The Hinterlands,Duskwood or Feralas...The portal is for Emerald Dream but that area is not open and maby won't be open.I have been there on private server and it is like some BIG green place with no mobs...Check youtube to see that place.