He would develop a fixation on unattainable women, often the wives of high ranking men. He would insinuate himself into the lives of his victims before using his ability to kill the entire family. This was due to his frustration from his inability to act or show his affection towards the object of his fixation in a healthy way.
During the episode Scully finds out that a person in the UK with this name has died two times under hot and strange circumstances. The first person was a kid that apparently was burned alive during a satanic ritual sometime in the '60s. The second person died in 1971 in a terrible fire. In the end of the episode L'Ively spontaneously catches fire and recovers "miraculously" fast in a military hospital. On asked how they can help him further, L'Ively responds to the nurse that he would die for a cigarette.
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