Helian Chang
In 429, Helian Chang was effectively used as a witness at the imperial advisory council, for the prime minister Cui Hao as he confronted astrologers Zhang Yuan (張淵) and Xu Bian (徐辯), who were advising against a campaign against Rouran, which Cui advocated. The astrologers, who were previously Xia court astrologers, argued that the stars were favoring Rouran and that a campaign would be fruitless. Cui, himself an astrologer, pointed out that if Zhang and Xu could predict the future, then they should have warned Helian Chang, who was present at the council as well, before Tongwan fell—that if they knew what would happen and did not warn Helian Chang, then they were unfaithful; if they did not know what would happen, then they had no prophetic abilities. With Helian Chang present, Zhang and Xu knew that he would confirm that they never informed him of impending doom, and so they withdrew their opposition.