Besides his heritage, Sima Yao was best known for his role in the death of Wen Yang, and his further involvement in the War of the Eight Princes during the reign of his cousin's son, Emperor Hui of Jin.
Yao was made Duke of Dong'an on 22 December 289 during his cousin Emperor Wu's last bestowment of titles to members of the Sima clan;[7] he was probably in his 20s at the time.
The cronies of Empress Jia Nanfeng then tortured Yang Yao, causing him to cry out in agony.
For that night, punishments and rewards arising from the coup were all handled by Sima Yao, and his fame grew.
[12] By the time Sima Yao was reappointed Prince of Dong'an in c.November 301, the situation in both the Jin court and the empire itself had changed dramatically.
In the northwest, Qi Wannian's rebellion had been quelled for about two and a half years, but the refugee situation it created continued to simmer.
[15] The next mention of Sima Yao was in August 304, where he was at Yecheng for the funeral of his mother Princess Dowager Zhuge.
Sima Yao told Ying, "Now that the Son of Heaven is leading the attack, it is best to disarm, don mourning clothing and leave the city to receive him and ask for forgiveness."