 Upon reaching the Lake of the Moon , the group captures and retains an enormous stationary cannon called a " Fixed Gun " from a Circle 's town across their fort . Using the Fixed Gun , Lizzie 's fleet of fire ships made from captured treasure ships loaded with Sahin 's explosives , and Morgan 's ground forces holding off the Circle 's elite Boneguard , they destroy the Fountain . As damage to the Fountain increases , Alain Magnan personally leads a force of Boneguard in a counterattack and is killed during the fighting . 
