Dongseong appears to have been promoted to the throne by the Jin clan, which prevailed over Hae Gu's rebellion.
He worked to strengthen the court's power after the move of the capital from the present-day Seoul area to Ungjin.
He incorporated the local Sa, Yeon, and Baek clans into the court to counter the entrenched aristocracy from the former capital.
The Book of Qi states that Dongseong sent armies to Liaodong and Liaoxi (요서 遼西) in China to defeat Goguryeo forces.
This caused great resentment, and Baek Ga's forces assassinated Dongseong while he was hunting.