the Mountain of Malefor is the epicenter of a cloak of shadow created by the Night of eternal darkness. the mountains' caves leak with blue-green acid, and is the weakest point in the force-field surrounding the Realm of Convexity. The semi-volcanic mountain is geologically unstable, though it's volcanic nature is held in check by the acid that flows under the mountain, itself having the same properties as lava.
The Legend of Cynder: The Precursor Legacy
The Mountain makes it's first-and only appearance in the novel, with Spiril having increasingly horrific nightmares concerning the mountain.
Chapter 15: Chain of Memories
Chapter 19: Shadow of Spire-Back Mountain
After traveling through a tunnel from the Celestrial caves, Spiril arrives at a series of platforms leading to the ancient mountain fortress. After entering the throne room of the palace built there, Spiril is attacked by Cynder, who appears t have been corrupted again. She later reveals it to be a ruse to fool the real enemy, the ape king Gaul. when she attacks him, she is thrown against the wall of the mountain palace and incapacitated. After the confrontation with Gaul, the Palace collapses, Spiril using his time fury to form a crystal to protect them. The Catacombs are revealed to have been carved under the mountain; their instability partly caused by that of the mountain.