Complex sentence: Working their way to the source of lightning, the group ends up in NASA's "graveyard", a dumping ground for everything NASA no longer uses, they are confronted by the mummy and werewolf, which attack them without warning.
Split into simpler sentences: Working their way to the source of lightning, the group ends up in NASA's "graveyard", a dumping ground for everything NASA no longer uses. They are confronted by the mummy and werewolf, which attack them without warning.