Qwsp
Qwsp, also known as Quisp, was an imp-like being native to the Fifth Dimension. He has a brother named Quirk (possibly Qwrk), who is a criminal. Both tried to pass themselves off as Water Sprites, and Qwsp bedeviled Aquaman early in the hero's career with his tricksterish ways.
Qwsp disappeared for many years, but recently returned to see how Aquaman was doing. He also learned of the Fifth-Dimensional princes Yz (also known as the Thunderbolt) and Lkz, who were trapped on the Earth plane. Qwsp soon learned that Aquaman had changed much, becoming darker. The imp decided that he would change as well, and changed from a mischevious trickster to a malevolent threat.
Qwsp manipulated events to free Yz and Lkz, who began fighting one another- this caused mass chaos and destruction on Earth, and threw the Fifth Dimension into turmoil. He also threatened J.J. Thunder, the Thunderbolt's new master, and killed the hero Wildcat. (Fortunately, Wildcat had gained a mystical gift of nine lives back in 1945, and recovered.) However, Qwsp's part in the crisis was found out by the authorities of his native dimension. After Yz and Lkz were merged into the balanced Ylzkz, the new Thunderbolt, Qwsp was captured, and sentenced to "1 million infinities in an 8-dimensional maze."
