Complex sentence: There the barbarians easily defeat Hekkus's foot soldiers, but when Patch's mechanical fort appears, it proves to mimic one of their own greatest terrors, an animal called the "dnazd", and they flee in panic before it.
Split into simpler sentences: There the barbarians easily defeat Hekkus's foot soldiers, but then Patch's mechanical fort appears. It mimics one of their own greatest terrors, an animal called the "dnazd", and they flee in panic before it.