Complex sentence: The group battles Fei-Wang who reveals his goal: to use the power of the two Sakuras to revive Yūko, accidentally frozen in time by Clow to halt her death, therein achieving the "impossible" and proving himself Clow's superior.
Split into simpler sentences: The group battles Fei-Wang, who reveals that his goal is to revive Yūko who was accidentally frozen in time by Clow to keep her from dying. By reviving her using the powers contained within the two Sakuras, Fei-Wang will accomplish the "impossible" feat of reviving the dead, proving himself Clow's superior.