Where no tunnels reach, there can be found the closed cavern of Echolost. Vast in size, echoes chase each other across the wide space for eternity. Some are so complex that they may be considered creatures in their own right, though they could not exist outside the space of Echolost. One side of the cavern in particular, known as the Wall of Echoes, is special. It appears as a flat black expanse of dense, rocklike material. It absorbs any sound that falls upon it, then once again emits that sound minutes, hours, days, or sometimes many years later. Sages sometimes come here just to listen to the wall, hoping to hear whispers of knowledge long lost. The other major feature of the cavern, the Earthpool, is a basin of dust so fine that it appears to be liquid, though woe to those who mistake the pale dust for water.
Echolost is a planar touchstone, granting powers over earth to those who know its secrets.