Complex sentence: An overlooking Genshin explains that the fiends are looking to resurrect the Archfiend who is supposed to emerge from Mount Fuji back in Japan the place which binded both the Black Spider Clan and The Dragon Lineage.
Split into simpler sentences: An overlooking Genshin explains that the fiends are looking to resurrect the Archfiend who is supposed to emerge from Mount Fuji back in Japan. The mountain is also the place which binded both the Black Spider Clan and The Dragon Lineage.