History: New Earth
E. Davis Ester of the planet Touston was bad luck personified. He caused jinxes wherever he went. He took the name Calamity King and journeyed to Earth. When he first applied for membership with the Legion of Super-Heroes, he shook Starboy's hand, possibly causing Thom's eventual expulsion from the Legion. Calamity King was denied membership, due to the fact that he would be as much a hazard to the team as he would be to enemies.
Pre-Zero Hour, 5 Year Gap Legion
In this alternate timeline, Calamity King became a full-fledged Legionnaire. After his initial rejection as a Legionnaire, Calamity King drifted from job to job, causing disasters wherever he went. When the Legion was desperate for new members, Calamity King noticed that the Legion were accepting some former rejects. He reapplied to the Legion and was accepted. The group disbanded two months later.
Calamity King along with many ex-Legionnaires, joined anti-Earthgov resistance, led by Jacques Foccart. Calamity King served as a double agent, causing trouble for Earthgov on the inside. He was discovered however, and sent to the Dominators underground experimental chambers. It is unknown if he survived the destruction of the chambers or the destruction of Earth.
Calamity King has the power to cause bad luck both physically or mentally to those around him. His bad luck effects both the animate and inanimate objects. It appears he has no control over this effect.