Riko and Reg have left the Seeker Camp and ventured further into the Abyss! The mysteries and peril that await them are the stuff of nightmares-but these nightmares are ruthless, deadly and very real. Do they have the courage and strength to survive as they descend into the deeper layers?

In an age when the corners of the world have been scoured for their secrets, only one place remains unexplored - a massive cave system known as the Abyss. Those who traverse its endless pits and labyrinth-like tunnels are known as Cave Raiders. A young orphan named Rico dreams of following in her mother's footsteps as a Cave Raider, and when she meets a strange robot when exploring the Abyss, she's one step closer to achieving her goal!

"So close, yet so far. The trio have arrived at Ido Front! The depths' sixth layer is almost within reach, but getting there is easier said than done. Before they can continue their journey, they have to get past the Sovereign of Dawn: Bondrewd!"--Provided by publisher.