The Sand Superman
The Sand Superman (sometimes referred to as the "Sand Thing", the "Sand Creature", and the "Sandman Superman") is an entity consisting of psychic energy from Quarrm, soil from Earth, and power siphoned from Superman. Neither entirely human nor villainous, the story of this being is chronicled in Superman No. 233 and 238 and Superman No. 240 through 242. The existence of the sand being on Earth causes many problems for Superman, as he deals with the ramifications of lost powers and injuries (including brain damage) resulting from them.
Created from a temporary portal between Earth and the Quarrm dimension during an explosion (S No. 233/1, Jan 1971: "Superman Breaks Loose"), the Sand Superman is initially mainly interested in draining power and knowledge from Superman for its own sake. However, as it gains and loses energy during its existence, it comes to more and more take on a desire to act as Superman does, as a being that serves unselfishly as a super-hero. However, two things make it impossible for the Sand Superman to remain on an Earth with Superman, the fact that it takes on power only when Superman loses it and the fact that because it is composed of alternatively-charged atoms—any contact with the Man of Steel would result in a cataclysmic explosion that would destroy the planet.
The mystic philosopher I-Ching puts Superman and the Sand Superman into a trance where they see the destructive results of a direct conflict between them. Because of this, the Sand Superman returns to the Quarrm dimensional realm, but as a result it takes about 1/3 of Superman's total powers and abilities with him, at least for a time (S No. 242/1, Sep 1971: "The Ultimate Battle").