The wraiths were a telepathic, shapeshifting species, indigenous to the planet Dakala. They were regularly hunted by the Eska. Young wraiths were more likely to become anxious than older members of the species. The shapeshifting powers of a wraith were very formidable. For example, if they became a rock, sensors were unable to tell the difference between them and a real rock. Wraiths were able to transform into anything seen by a person whose thoughts they sensed, such as a tree, an animal, water, or even an imagined humanoid. Biologically, if cells were separated from a wraith's body, they were then perpetually in a state of chromosomal flux, as if the cells were constantly attempting to mutate into something but couldn't decide what. (ENT: "Rogue Planet")
Once, a group of wraiths were pursued by a team of nine hunters – Eska visitors to Dakala – into a blind canyon. Though at least one of the hunters fully expected the wraiths would be easily killed and had no way to escape, the wraiths had read the minds of the hunters, knew their plan, and were well prepared when they arrived. The incident was a decisive victory for the wraiths, with only three Eska ultimately surviving.
The wraiths killed more Eska than vice versa until the Eska discovered that cornering them and thereby causing the wraiths to panic caused them to emit a chemical signature which could be tracked. In essence, the wraiths consequently lost the advantage which their own transformative abilities had given them.
A few years later, Captain Jonathan Archer and the crew of Enterprise NX-01, while visiting Dakala in 2151, initially didn't detect any evidence of the humanoid forms which the wraiths could assume. After the newcomers came upon a group of three Eska hunters, however, one of the wraiths appeared to Archer as a mysterious Human woman he felt sure he recognized and was involuntarily drawn to; she had read his mind and taken the form of the "glimmering girl" in Yeats' The Song of the Wandering Aengus, just as he had imagined her when he was a child. She explained that her people were telepathic shapeshifters, being hunted by the Eska.
Dr. Phlox made a compound that masked the chemical signature of the wraiths, which concealed them from the hunters' sensors and ensured the wraiths would be safe. The compound was administered to all the wraith by the same one which had been in communication with Archer. While one of the wraiths was being hunted by the three Eska, numerous members of the heretofore hunted species surrounded the Eska and scared them away with loud growling noises. Thereafter, Archer's mysterious friend thanked him, said goodbye, and let him see her true form. (ENT: "Rogue Planet")
Background information Edit
In the final draft script for "Rogue Planet", the female guise of the wraith which Archer encounters is initially described as "A Human woman lit in the starlight. She's beautiful and ethereal – as if she's a part of the jungle itself. She's wearing a slight, diaphanous dress." A subsequent description of her voiced by Archer was scripted to include a mention of her having "long dark hair," though her hair color was changed to blonde in the episode. There were repeated mentions, in the script, of her being "lit by starlight."
The unnamed wraith woman was played by Stephanie Niznik.
In the script of "Rogue Planet", a wraith in its natural configuration, initially viewed through a pair of Eska imaging goggles, was described thus; "A strange amorphous signature. It doesn't have a definite shape, and it vanishes into the jungle as quickly as it appeared. (NOTE: This signature should glow with a unique effect, different from the spectral image of the drayjin, indicating it is something called a 'wraith'.)" Cellular residue from a wraith was scripted as "strange alien cells that seem to be constantly mutating." In the final scene of the episode, the script described the wraith as "something utterly alien" and "a glistening, inhuman creature."