Fathom: Dawn of War bridges the gap between the original series and Fathom vol. 2. The story focuses on the Blue warrior Kiani, who is forced to side with the rebellious councilman Marqueses in order to save her master, Casque, from the clutches of human military scientists. Marqueses has engineered the situation in order to kidnap Casque and to secure the older warrior’s immense power for an offensive against the humans. Kiani tracks down Marqueses and saves Casque only to find he is part of the Black. The Black come for Casque, and he is forced to rejoin them, leaving Kiani angry and lost.
Dawn of War emphasizes Kiani’s loneliness and character development. It also introduces audiences further to the underwater world of the Blue.