What The Ice Left Behind - Bound By Ruin

After surviving impossible odds, Illinois, Leviathan, Hunter, and Dr. Jericho find themselves facing a mystery that threatens everything they thought they understood about the frozen world around them. When a strange mutant named Eclipse arrives with unsettling knowledge about the infection, Illinois is forced to confront a terrifying possibility: she may not be like the others. As forgotten secrets emerge from abandoned laboratories and monsters begin hunting with purpose instead of instinct, one truth becomes impossible to ignore. Something isn't just watching Illinois. It's searching for her. While Leviathan struggles against the ghosts of her past and the bond between her and Illinois grows stronger, the group uncovers clues that connect the mutants, the infection, and a far greater force lurking beneath the ice. Every answer comes with a cost, and every step forward pushes them closer to a truth that could change their world forever.  

(3rd book)