Complex sentence: Metatron is the Regent of Heaven and the true antagonist of His Dark Materials, and seeks to supplant the Authority, destroy Lord Asriel and his army, and kill the heroine Lyra Belacqua.
Split into simpler sentences: Metatron is the Regent of Heaven and the ultimate antagonist of His Dark Materials. He seeks to supplant the Authority, destroy Lord Asriel and his army, and kill the heroine Lyra Belacqua.