Originally the Chief Archivist on Gallifrey, he grudgingly welcomed a young Caleera to the department, offering her a very low-ranking position (under Padrac's advisement). Like many of his brethren, he was concerned she was unstable due to her now-latent immense psychic potential. Caleera bore a grudge for years and after she was manipulated by the Eleven, she used her returned abilities to punish Sternbar. She then 'recruited' him along with Sepulchra and Swordfish to act as helpers in her efforts to expand her abilities even further.
By the time the Doctor arrived, he had taken to calling himself "Lord Stormblood", and had been pushed beyond the limits of his sanity through exposure to the time winds, since the TARDIS had badly degraded, losing its outer shell completely. He remembered enough to still help with the experiments, and that it used Caleera's own psychic powers. Once Caleera was free, she lowered the TARDIS shields, allowing Stormblood and his companions the death they longed for, sending them falling into the vortex. (AUDIO: Scenes From Her Life)