The Fulgur: The Burnt Lands (The Fulgur #3)

Trapped in an underground cave, Claudian and his comrades have found two new survivors. But with supplies running low, their small group will need to find a way to get back to the surface... An immense volcanic shaft is discovered in the walls of quartz... Is it the way to freedom? At the risk of their lives, two volunteers undertake an extremely perilous ascent!