Complex sentence: One day, while exploring the cave's extensive network of tunnels, the man encountered a sleeping dragon who awoke upon his entrance--he feared that the dragon would incinerate him with its fiery breath; instead, the dragon knelt before him and obeyed his commands.
Split into simpler sentences: One day, while exploring the cave's extensive network of tunnels, the man encountered a sleeping dragon who awoke upon his entrance. He feared the dragon would incinerate him with its fiery breath, but the dragon instead knelt before him and obeyed his commands.