Complex sentence: The magic circles and fickle winds of magic granting favours to the strong and deserting the weak, the Giants broke apart stone circles and other creatures, and the mighty Fen Beasts attacked all who would defy their master's will.
Split into simpler sentences: The magic circles and fickle winds of magic granting favours to the strong and deserting the weak. And the mighty Fen Beasts attacked all who would defy their master's will.