Complex sentence: The first step is to cross a strange land with a mad-scientist laboratory and Frankenstein-esque theme to it, subsequently diving into an aquatic breeding laboratory, presumably one of the main locations where the gill beasts are grown by the Cabal.
Split into simpler sentences: The first step is to cross a strange land with a mad-scientist laboratory and a theme reminiscent of "Frankenstein". He subsequently dives into an aquatic breeding laboratory, presumably one of the main locations where the gill beasts are grown by the Cabal.