Sato Katsura Sato Katsura , also known as Katsura Sato ( Westernised name ) or Cardinal Morningstar ( long - term alias ) , was originally a Japan ese samurai warrior . His contact with various extraterrestrial forces led his life onto a very different path , where for many years he worked as an agent of . Biography . Mortal life . As a samurai Sato served the Lord of Clan Makoto . He was a dedicated and highly skilled warrior , but his commitment to an honourable life was probably his over - riding motive . When Lord Makoto was killed by what appeared to be demons bearing the crest of the rival Clan Rikushira , Sato pledged himself to avenge his master and then commit suicide ( feeling he had failed by allowing him to be killed ) . On the way to Castle Rikushira , he encountered Izzy , and with her help was able to enter the fortress . Lord Rikushira had entered into an alliance with aliens known as the Gaijin . However , the vision of Japan ' s future that Rikushira ' s mother Asami was able to extract from Izzy ' s mind drove her insane and she used the alien technology the Gaijin had provided ( source of the demons that had killed Makoto ) to destroy the castle , planning to launch a pre - emptive attack on the West to prevent the atom bombings of the 20th century . The Eighth Doctor persuaded the Gaijin to stop Asami , and in the chaos Sato was able to kill Rikushira . He was mortally wounded , however , and would have died had the Doctor not treated him with life - preserving nano - drones the Gaijin had supplied Rikushira with as part of their deal . However , to his horror , Sato discovered that the nano - drones could not be deactivated and his attempts to commit honourable suicide , now that his mission was fulfilled , were futile . He was effectively immortal and invincible , but at the same time had lost the thing that mattered most to him : his honour . For Izzy ' s sake he did not kill the Doctor , but left the time travellers , an angry , bitter man . ( COMIC : " The Road to Hell " ) Immortal servant of the Master . Sato became a pirate but tired of this and enabled himself to be captured . The Spanish Inquisition were unable to kill him , so imprisoned him in Saragossa for 50 years . Sato was granted the chance to take revenge on the Doctor when he was contacted by . The renegade became a mentor to Sato as part of his plan to take control of The Glory . At the Master ' s behest , Sato adopted the identity of Cardinal Morningstar , leader of the Church of the Glorious Dead . The Church launched a relentless holy war which perverted the natural course of Earth history , Sato becoming absolute ruler at the beginning of the 19th century , and led to the planet becoming known as Dhakan . By the 20th century Earth had mastered interstellar travel . To weaken the Doctor ' s resolve prior to their battle for the Glory , the Master had Sato destroy the civilisation of the planet Paradost with the help of Ash Wraiths . The Doctor ' s companions Izzy and eventually destroyed the Wraiths , but Sato was able to shoot Izzy with a TCE and take her captive . With his prisoner ( and , unbeknownst to him , Kroton aboard his ship as a stowaway ) , Sato returned to Dhakan , where he believed the Master ' s final victory over the Doctor was imminent . However , the battle for the Glory was not between the Doctor and the Master , as everyone had assumed , but between Sato and Kroton . Sato ' s warrior skills and immunity meant he outmatched even the power of a Cyberman , but Izzy had managed to free herself and forced Sato to take a mnemonic crystal , confronting him with all the suffering he had caused and breaking his will . Kroton , however , was able to take the crystal and confront his memories , rendering him the victor of the duel . With this , Kroton was placed as the overseer of the Glory and granted Sato the honourable death that he had always wanted , as well as repairing the damage Sato had done to Earth ' s history . ( COMIC : " The Glorious Dead " )