Complex sentence: Kingson squares off against Cort in a competition of riddles, and appears to win the competition, but Cort accuses him of substituting Vannay's scrolls with ones that Kingson himself copied from older texts with poorly thought out, incorrect answers.
Split into simpler sentences: Kingson squares off against Cort in a competition of riddles, and appears to win the competition. After the competition Cort accuses him of substituting Vannay's scrolls with ones that Kingson himself copied from older texts with poorly thought out, incorrect answers.