The Peregrine was Oser's personal ship. In the years before the Dendarii took over Oser's fleet, he had used the Peregrine as his flagship. When Miles Vorkosigan created the Dendarii Free Mercenary Fleet from Oser's ships, he used the Triumph as his own flagship. Later, when Oser took back over the fleet, he kept the flagship as the Triumph.
After Oser's death, the ship was owned by the fleet. Miles eventually gave the captaincy to Elena Bothari-Jesek. Soon afterwards, he took the Peregrine to Jackson's Whole chasing Mark Vorkosigan and Bel Thorne on the Ariel because he needed the fastest ship available, and Peregrine was the next fastest ship with significant firepower after Ariel and Jayhawk.