Sorrow's Furnace

Sorrow's Furnace is a new explorable area expected to be added to the game in the Summer 2005 Game Update, along with Grenth's Footprint.

Both Sorrow's Furnace and Grenth's Footprint are underground areas in the Shiverpeak Mountains.

Quoted from the E3 preview:
 * On the eastern slopes of Lornar's Pass, north of Camp Rankor rests the deep, slag-strewn expanse of Grenth's Footprint. Once a sacred place for the dwarves of Deldrimor, the peak itself has been completely dismantled, and the land torn open to get at the precious metals beneath the soil. The Stone Summit have dug deep into the Shiverpeak Mountains. Underneath the stripped, barren land, are the all-but-depleted mining shafts of Sorrow's Furnace.

Considering that the area of Lornar's Pass is an area for advanced players, with most of the monsters in this area being level 20 or higher we can excpect Sorrow's Furnace and Grenth's Footprint to be just as tough or tougher.