Complex sentence: A version of the three crows is probably based on the three ravens folk tale where three crows plot to devour the corpse of a dead knight only to be thwarted by the knight's hawk, hound and mistress.
Split into simpler sentences: A version of the three crows is probably based on the three ravens folk tale where three crows plot to devour the corpse of a dead knight. Then they are thwarted by the knight's hawk, hound and mistress.