The Torajenn originally had regular mammalian humanoid bodies. This all changed in the early 20th century when exposure to radiation from one of their wars stripped the Torajenn of their flesh. All that physically remained of the Torajenn was their skeletons, but they managed to preserve themselves by becoming energy matrices.
In 1941, they attracted the attention of Susini, who saw their plight as a way of gathering materials for her necrotist art. On the Day of the Dead, the Torajenn and Susini landed in Coyoacan to gather flesh from the humans to use to restore the Torajenn to their former selves. The Torajenn projected light-patterns from photographs onto their force fields to masquerade themselves as loved ones of the humans. Once the humans trusted a Torajenn, it would psionicaly tear the flesh from their bones and bring the skeleton back to Susini.
Upon learning of this scheme, the Eighth Doctor confronted the Torajenn and Susini. He used Susini's ultrasonic projector to emit a sound so high-pitched that the Torajenn were unable to concentrate on maintaining their force fields. With their plasma matrices exposed, the Torajenn were all torn apart. (COMIC: The Way of All Flesh)