Trix MacMillan

Biography
Beatrix "Trix" MacMillan was a con artist. When she first met the Doctor, she had been hired by Sabbath to pose as a descendant of Tsar Nicholas II. She stowed away in the TARDIS, avoiding detection by the Doctor and his companions for a long while.

Trix often disagreed with the Doctor, however over time the Doctor taught Trix how to come to terms with herself and feel settled in her life. Trix's last appearance was in The Gallifrey Chronicles where she joined hands with the Doctor and Fitz and then jumped into the central hive of the Vore.