Complex sentence: Later, Azulongmon would drive BlackWarGreymon to destroy the Destiny Stones (Holy Stones), which kept the balance of the Digital World intact, by accident because after a stones would be destroyed, it would cause Azulongmon to appear briefly in pain.
Split into simpler sentences: Later, Azulongmon would drive BlackWarGreymon to destroy the Destiny Stones (Holy Stones), which kept the balance of the Digital World intact, by accident. This is because after a stone was destroyed, it would cause Azulongmon to appear briefly in pain.