Bio: A species of shapeshifters, the Gwanzulum nearly destroyed the Whifferdills (Frobisher's race) during the Shaper Wars. The last remaining Gwanzulum ended up stranded on the planet Adeki. There, they drained the life out of the indigenous population (a natural result of their kind of shapeshifting), and lay in wait for passersby.
When the Seventh Doctor happened upon the planet, the Gwanzulum had a virtual feast of all the Doctor's life-energies. Before long, they masqueraded as the Doctor's past lives, as well as several of his past companions.
In the end, the Seventh Doctor merely got in his TARDIS and left the Gwanzulum to find some other life to bother.