- "The owner of the second voice also wore dress greens, more heavily encrusted with gilt than any she had ever seen. Jeweled decorations on his breast glinted and winked like lizards' eyes in the light from Vorkosigan's desk lamp. He was about thirty, black haired, with a rectangular tense face, hooded eyes, and thin lips compressed now with annoyance."
- ―Prince Serg as seen by Cordelia[src]
Serg was married to Kareen, who bore him a son, Gregor Vorbarra. However, her marriage became intolerable as Serg became more and more mentally unstable, and became a protege of sorts to Ges Vorrutyer. In addition, his ambitions were stoked and manipulated by Minister of Political Education Grishnov. He attempted to assassinate his father twice to rise to power prematurely.
- "I will not sicken you with the details of Negri's reports... But the Emperor said if it wasn't done now, we would all be trying to do it ourselves, five or ten years down the road, and probably botching the job and getting friends killed, in a full-scale civil war."
- ―Aral Vorkosigan[src]
It was at this point Ezar and Chief Negri began to formulate a plan to remove Prince Serg as well as his flunkies and sycophants. When they realized that the Escobarans had discovered Barrayar's invasion plans, and that the Betans had invented a secret new weapon, plasma mirrors, they coerced Aral Vorkosigan into helping them create a situation in which Serg and his followers would be killed; Vorkosigan stoked Serg's desire to lead his forces into battle. The plan was successful - Serg and Grishnov were destroyed when they were attacked by the state-of-the-art weapon that the Barrayarans had no answer for. Vorrutyer, who had been intended as a scapegoat for the failed invasion, was killed by Konstantine Bothari instead. Vorkosigan, placed in a position to assume command of the fleet when Serg and the rest of his followers were killed, coordinated a retreat.
Prince Serg was viewed as a hero in battle by most of Barrayar, a martyr who died in combat - the advanced Barrayaran dreadnought, the Prince Serg, was named after him, as was the Barrayaran planetary colony Sergyar. To the rest of the galaxy, Serg was viewed as a psychotic, which was actually the truth; this came as a shock to Elena Bothari when she saw the historical holofilm The Thin Blue Line.
When Emperor Gregor was old enough, he learned Serg's true nature which sent him into a deep depression and attempted suicide, thinking he was sure to end up following Serg and Yuri Vorbarra into madness.