Complex sentence: Price's dichotomy dictates the second stage commenced with August Derleth, the principal difference between Lovecraft and Derleth being the latter's use of hope and that the Cthulhu mythos essentially represented a struggle between good and evil.
Split into simpler sentences: Price's dichotomy dictates the second stage commenced with August Derleth. The principal difference between Lovecraft and Derleth being the latter's use of hope and that the Cthulhu mythos essentially represented a struggle between good and evil.