Complex sentence: Her hostility and the forest's cataclysm are explained in flashbacks: when Ori was lost, the Spirit Tree released a flash of light in order to look for him, which killed all of Kuro's recently hatched offspring.
Split into simpler sentences: Her hostility and the forest's cataclysm are explained in flashbacks. When Ori was lost, the Spirit Tree released a flash of light in order to look for him, which killed all of Kuro's recently hatched offspring.