This portal gate is level restricted. Your character has to be level 45 to get in. Once you get to 45, you pick up the available to everyone Epic Line - Volume 2, Book 1. Go thru the portal. Complete Book 1 which opens the door to get into Moria. Moria is both level and quest locked. Without the Moria unlock there is no way to walk to the Great River, Lothlorien or Mirkwood regions.
Originally Posted by Haderus
East Angmar is another level and quest locked area. Characters that have not completed the unlock sequence are instantly killed every time they try to enter East Angmar. Again it is a Epic book. Volume 1, Book 6 in this case. Mirkwood is a third level and quest locked area.
Both Mirkwood and Moria were implemented this way in order to keep the server from crashing when these two expansion packs went live and hundreds of people flooded the area to access the new content. Turbine developed a better of method of handling land rushes after Mirkwood.
Unless stated otherwise, all content in this post is My Personal Opinion.