Sanctum Somnium is one of 13 zones being introduced with the House of Thule expansion in October. Here's a preview of the zone from EQLive:

Sanctum Somnium

This is the home of the Lord of Dreams, Morrell Thule. The Sanctum is the center of his realm, the Plane of Dreams where Morrell oversees all that happens in our subconscious. Here, in his base of power, Morrell has collected the manifestations of our dreams. Things that should be familiar, yet somehow are not, contribute to the wonder and mystery of this dream world.

Here, at the heart of the Plane of Dreams, anything can happen. Morrell's home is the source of fantasy itself and contains elements of the varied fantasy realms dreamt up by Norrath's citizens. Time and space can be easily reshaped here. But beware, adventurers, not all dreams are happy and light. Nightmares also dwell in this realm.
 
Morrell Thule keeps his rooms at the very top of the tallest tower. From this lofty position he presides over his realm, directing the dreams and nightmares of mortals. His servants inhabit the lower levels of the tower, tending to his needs and attending their duties. There are others who dwell in Morrell's tower. The unfortunate few who have been trapped in their dreams...

You can check out a few more screenshots of Sanctum Somnium over at EQLive.