Batman (Earth-B)

Batman was the sworn protector of Gotham City on Earth-B, an alternate reality on a parallel earth.

History
As a boy, Bruce Wayne witnessed his parents' gruesome murder by an unknown gunman in Gotham City on Earth-B and vowed revenge against all who broke the law. Bruce Wayne was the second son of Thomas and Martha Wayne, the other being his older brother, Thomas Wayne, Jr. Bruce's father was a well respected Gotham doctor, and his mother a homemaker. Thomas and Martha Wayne were very influential in Bruce's early life, instilling thoughts of truth and honesty. When his parents were murdered, Bruce was devastated. As a young adult, he worked to fulfill this vow by traveling the world to learn from masters of various defense disciplines. Eventually he became an exceptional escape artist, master of martial arts, acrobatics, science, technology, boxing, disguises, criminology and detective skills. Having perfected his skills, Bruce returned to Gotham City. However, he came to realize that his skills were not enough, that he would need an edge over his opponents -- a guise that would strike terror into their hearts. Inspired by the bats that had so horrified him as a boy, Bruce donned a blue-and-gray costume complete with cape and cowl and renewed his mission.

Bound by his personal code of justice, Batman resolves to never kill an enemy. Instead, he relies on his physical prowess and mental superiority to bring his enemies to justice.

Over the years, the Batman of Earth-B has faced many insane homicidal killers in his war on crime, including the murderous Catwoman and the maniacal Cavalier.

Behind the scenes
This alternate universe of Earth-B was never specifically depicted, but was suggested to exist in a letters column by DC editor/writer Bob Rozakis as a possible explanation for certain non-continuity stories or character traits (for example, stories that showed Catwoman committing murder with no qualms, despite being established that she did not engage in that kind of activity). ICG's Official Crisis Cross-over Index theorized that DC Challenge took place on this earth which given the involvement of Oan Guardians would make it an alternate Earth-One timeline. Following the Crisis on Infinite Earths, Earth-B stories with Batman continued, possibly designating Earth-B as a simply inaccessible dimension that continued to exist somehow unaffected by the multiversal crisis.