The Companion is a cloudlike life form that lived on a planetoid in the Gamma Canaris
Region. In 2117, the Companion discovered aged scientist Zefram Cochrane drifting in space, near death. The Companion brought Cochrane to her planetoid and cared for him, rejuvenating his body, giving him effective immortality, but subjecting him to extreme loneliness. Over time, the Companion grew to love Cochrane. In 2267, the Companion abducted Kirk, Spock, McCoy, and Federation commissioner Nancy Hedford from the Enterprise shuttlecraft Galileo to live with Cochrane to alleviate his isolation. Hedford, terminally ill with Sakuro's disease, agreed to merge with the Companion, becoming a single, human individual. The resulting individual, still in love with Cochrane, remained with Cochrane on the planetoid for the rest of a normal human lifetime.
The Companion Can Be Seen In The Episode, "Metamorphosis."