Complex sentence: Wander requests that Dormin return Mono's soul to her body, which it states may be possible on the condition that Wander can destroy the sixteen idols lining the temple's hall by using the ancient sword to kill the sixteen colossi located throughout the land.
Split into simpler sentences: Wander requests that Dormin return Mono's soul to her body, which it states may be possible, but only if the sixteen idols lining the temple's hall are destroyed. It explains that this task can only be accomplished by using the ancient sword to kill sixteen colossi located throughout the land.