Complex sentence: The Doctor then devises the only method of combating the Mara, since evil cannot face is itself, he organizes the construction of a large circle of mirrors (actually reflective solar panels) in a jungle clearing.
Split into simpler sentences: The Doctor then devises the only method of combating the Mara. Since the one thing evil cannot face is itself, he organizes the construction of a large circle of mirrors (actually reflective solar panels) in a jungle clearing.