Complex sentence: Koga forces Mori to tell him the location of the Cave of Gold; an urban legend which the sword and dagger are the keys to open, fearing the safety for his grandchildren, Mori agrees to aid Koga.
Split into simpler sentences: Koga forces Mori to tell him the location of the Cave of Gold; an urban legend which the sword and dagger are the keys to open. Fearing the safety for his grandchildren, Mori agrees to aid Koga.