Parasite

Parasite is an enemy of Superman who feeds on energy by hungrily absorbing it into his body, draining all living creatures into husks at his touch. Because of the massive danger he presents to anyone he comes into contact with, he spends most of his time imprisoned in Stryker's Island Penitentiary. For normal humans, he is deadly. For metahumans and aliens with more energy to spare, he is still potentially deadly, but usually does not fully drain them, preferring to use them as a 'battery' since the powers and energy he absorbs from them don't last long.

Rudolph Jones was a slacker, transformed while working as a janitorial labourer at a Pittsburgh's S.T.A.R. Labs facility. Thinking a waste container might have held something valuable he opened it and was exposed to strange radiation that changed his body. Jones now had the ability to absorb the life energy of other people leaving withered corpses. Eventually a scientist that was tending Rudy was tricked and ultimately absorbed into the Parasite. This joining was different than Rudy's others; he actually retained the scientist, Dr. Torval Freeman, as a part of his own mind.

Dr. Torval Freeman was one of the Parasite's victims who, unlike many of Parasite's other victims, was absorbed into Parasite and actually was retained as part of the Parasite's own mind (along with Rudy Jones).