伍子胥 / Wu Zixu
伍子胥 / Wu Zixu enters the wiki through 《资治通鉴·周纪》80丨诸葛亮的偶像 到底有多厉害？ as the historical warning 乐毅 uses in 《报燕惠王书》. The episode says Wu Zixu helped King Helu of Wu build major achievements, but later 吴王夫差 ignored his advice, gave him a sword, forced him to die, and threw his body into the river.
The source does not develop Wu Zixu as a full biography. His role is comparative: he shows why a minister cannot assume that service under one ruler remains safe under a successor. For Le Yi, the lesson is that honoring 燕昭王 does not require returning to 燕惠王 after suspicion and removal have already made the court dangerous.