Complex sentence: Kronos himself was damned to eternal suffering, bound by Zeus's lightning, but after thousands of years, with the seals growing weak, Kronos became able to project his will to any part of Earth in the form of a giant being with six arms.
Split into simpler sentences: Kronos himself was damned to eternal suffering, bound by Zeus's lightning. After thousands of years, with the seals growing weak, Kronos became able to project his will to any part of Earth in the form of a giant being with six arms.