Old Blue had an intimidating appearance but was friendly and had no courage, and so was useless as a guard dog. Rastin had originally intended him to be a beast of burden, hauling mineral samples. In the end however, he was only good as a companion, an exception to the prospector's dislike of company.
During the zerg invasion of Bhekar Ro, Old Blue was attacked and infested by a queen, transforming into a roverlisk. When colonist Octavia Bren came to visit, Old Blue attacked her, and later exploded in an effort to kill her.
Old Blue's genetics were used as the basis for more roverlisks.