Diabolus Darkdoom is father of H.I.V.E. student Nigel Darkdoom, he is presumed to be dead, executed by Number One, for so called treason, a fact known only to a select few. In Escape Velocity he appears onboard his massive cutting-edge submarine created by and for him and his crew, called the Megaldoon, he rescues Raven and gives her the means to get to H.I.V.E. and rescue Otto, Shelby, Wing and Laura who are about to be shipped off to Number One (a.k.a Overlord).
Diabolus then provides them with the tech needed to get them into MI6 Deepcore and joins them when they launch a rescue attempt for Dr. Nero who has been captured by a ruthless organisation called H.O.P.E. led by an evil man called Sebastian Trent. At the end of the book after Overlord's body is destroyed Diabolus is gived the postition of G.L.O.V.E. council leader
In Escape Velocity