Complex sentence: Inside the cave network she finds a dying Cameo, who tells her the Beforetime weapons Alexi and Vega are searching for caused the Great White, but they do not know this; and that it is Elspeth's destiny, as the Seeker, to destroy them.
Split into simpler sentences: Inside the cave network she finds a dying Cameo, who tells her the Beforetime weapons Alexi and Vega are searching for caused the Great White, but they do not know this. She also reveals it is Elspeth's destiny, as the Seeker, to destroy them.