Hsien-Ko was the daughter of Li H'sen Chang. While still in the womb in 1872, she was irradiated with chronon radiation by the arrival of Magnus Greel's time cabinet. This rendered her sterile, but also slowed her ageing. By 1937, though she was 65, she only looked as though she were in her twenties. She could also sense and navigate the Dragon Paths. She used her blood to create geomantic compasses that allowed her followers to use the Dragon Paths as well.
Hsien-Ko planned to get revenge for her father's death, finding and repairing Mr Sin to aid her. With knowledge gained from her father's notes, she was going to divert Magnus Greel's zygma beam so he would arrive in 1937 Shanghai instead of 1872 China. Once there, she was going to put him in a modified organic distillation cabinet so he would exist, barely alive, in agony forever. The Fourth Doctor tried to persuade her not to carry out her plan, since it would result in her father never meeting Greel and herself never getting infused with chronon radiation. The result would be a temporal paradox centred on her.
However, she ignored the Doctor's warnings. To return Greel's cabinet to its original destination, the Doctor time rammed it with his TARDIS. The chronon feedback from this went through Hsien-Ko and she was disintegrated. (PROSE: The Shadow of Weng-Chiang)