Complex sentence: When Damian leaves to deal with a new crisis, Elliot surmises that Firefly is the villain behind the attack, notes how Gotham has fallen apart in Bruce's absence, and ponders how to use this to his advantage.
Split into simpler sentences: When Damian leaves to deal with a new crisis, Elliot surmises that Firefly is behind the attack. He notes how Gotham City has fallen apart in Batman's absence, and ponders how to use this to his advantage.