The Abyss of Death was a stratum of Skaro located above the Morass and below the Depths of Unknown, being the fifth stratum from the surface. The Fissure passed through it.
It was made of living rock that could feel hunger. Anyone that ventured through the tunnels of this stratum would likely be eaten by the walls. (COMIC: The Dalek Trap [+]Loading...["The Dalek Trap (comic story)"])