Complex sentence: In the meantime the project grew as Marquis added details of Wooden Leg's life before and after the events at the Little Bighorn and eventually metamorphosed from a historical account of the battle into a biography of Wooden Leg, Marquis' principal informant.
Split into simpler sentences: In the meantime the project grew as Marquis added details of Wooden Leg's life before and after the events at the Little Bighorn. It eventually metamorphosed from a historical account of the battle into a biography of Wooden Leg, Marquis' principal informant.