In Jeff Long 's 1999 novel The Descent and its 2007 sequel Deeper Homo Hadalis .
The Descent and its 2007 sequel Deeper is a vast labyrinth of tunnels and passages underlying the Earth is inhabited by a brutal species of once - civilized but now degenerate hominid .
In Jeff Long 's 1999 novel The Descent and its 2007 sequel Deeper , a vast labyrinth of tunnels and passages underlying the Earth is inhabited by a brutal species of once - civilized but now degenerate hominid , Homo Hadalis .