Destrii

Biography
Destrii is a person of fish appearance. She is first found by the Eighth Doctor and Izzy in the stomach of Orphidus, the spaceship used by the after she is transported from Oblivion by her uncle Jodafra. She proceeds to steal Izzy's body and become apparently killed by one of the Morbox, a resident alien, in revenge for killing its mate. Destrii returns as a character in Uroborous, where she is found living wild and taken by the Doctor to help him find Izzy. She goes separate ways after Oblivion, where she and her uncle have powered up their time machine and escaped from the ruins of the planet. After this, Destrii returns in Bad Blood, where she stays with the Doctor until the end of his strips while in his Eighth incarnation, in The Flood. She also takes on a human holographic disguise in Sins of the Fathers, which resembles a young coloured girl not entirely unsimilar to Martha Jones in appearance.

Personality
Destrii is perhaps infamous for having a personality unlike many other companions: she takes a "fists first, brains second" approach. For a while she is portrayed as a villain after she steals Izzy's body, but is the taken on as a companion after Izzy leaves.