Cardinal Ollistra was a high ranking Time Lord involved in the Time War. A known associate of the War Doctor, her official title is unknown, only described as "arch-manipulator and Time Lord strategist".
During the Time War
Ollistra was present when a Gallifreyan reported the destruction of the Dalek fleet and the death of the Doctor. Horrified, Olistra laments Time Lord soldiers Bennus and Arverton when they allow the War Doctor to activate the Dalek Time Destructor instead of them, a blast no Time Lord can survive. Ollistra attends the Doctor's funeral, sceptical of his demise. With her strong belief that the Doctor was still alive, she sent Veklin to search for him. After gaining control of the Eye of Harmony of the Doctor's TARDIS, Ollistra pulled the Doctor from Keska when he refused to go home. (AUDIO: The Innocent)
She later built a team, consisting of the War Doctor, Veklin, Bennus and Arverton, to rescue Seratrix, a Time Lord strategist, in the "Null Zone". (AUDIO: The Thousand Worlds) It was later revealed that the scheme underneath the mission was to purge the idea of Seratrix to make peace with the Dalek. The reason why she sent the "rescue team" was because she believed that the Doctor, Bennus, and Arverton were followers of the belief of Seratrix so they should be killed together with him.
After the War Doctor stopped the plan of the Daleks to explode the thousand planets, Ollistra came and revealed her plan to the Doctor. After that, she brought the Doctor to the future of Keska to show how the planet recuperated from the invasion of the Daleks. (AUDIO: The Heart of the Battle)
Personality
Ollistra is constructed as a heartless politician. Bennus and Arverton joke over the existence of Ollistra's emotions. Ollistra is also presented as truly patriotic, allowing Gallifreyans to sacrifice themselves for the greater good. Ollistra presents a discontent with the Gallifreyan armed forces, telling two soldiers "The Doctor is worth a hundred of you... people!". One could argue that Ollistra has become morally corrupt following her involvement in the Time War, Ollistra vowed to destroy every Dalek before the Time War is over. (AUDIO: The Innocent)
Relationship with the War Doctor
Although Ollistra respects the Doctor's efforts for Gallifrey, she is also seen to despise him. Ollistra describes the Doctor as "a thorn in your side. An embarrassment for most of his lives." When he is presumed dead Ollistra confesses "Oh Doctor. I feel the universe is a far more dangerous place without you" commenting on either the Daleks' strength against the Time Lords or the freedom the Time Lords have to do the unthinkable and commit genocide themselves now the Doctor cannot stop them.(AUDIO: The Innocent)