Complex sentence: Claiming to be the rightful ruler of both the Moon Kingdom and the Earth, she first invades Elysion, which hosts the Earth's Golden Kingdom and captures its High Priest, Helios and instructs her followers to steal the Silver Crystal from Sailor Moon.
Split into simpler sentences: Claiming to be the rightful ruler of both the Moon Kingdom and the Earth, she first invades Elysion, which hosts the Earth's Golden Kingdom. She captures its High Priest, Helios, then instructs her followers to steal the Silver Crystal from Sailor Moon.