Michael Turner's Fathom. Killian's Tide

When Aspen Matthews came to discover her true heritage, and her life beneath the waves began, her first mentor was the vicious Killian, who intended to turn her into a weapon which would destroy the world above the water utterly. Now Titan Books present Killian's story. Years before Aspen's birth, there is dissent amongst the ocean-dwellers. One of their cities has been unwittingly destroyed by humans, as a result of an atomic test. Rival factions clash over the right way to proceed, but, it seems, none of them wish for an all-out war. Even those who distrust and dislike humans - Killian included - know that to attack would lead to discovery, and chaos beyond their most awful imaginings. But when Killian discovers the terrible truth behind his parents' deaths, everything changes...forever...