Orca

History
Grace Balin attends Gotham Gate college and quickly becomes fascinated with the ocean. She receives a Ph. D in Marine Biology and Bio-Medicine and takes a job at the Gotham Aquarium. She is a very charitable person who funds an after-school program involving the ocean for underprivileged youths. She also volunteers at a soup shelter and takes care of many homeless people. Dr. Balin is later involved in an accident that leaves her paralyzed, dependent on a wheelchair for mobility. She continues to work at the Gohtham Aquarium until it is supposed to be closed for lack of funding.

Grace experiments with spinal cord tissue regeneration using orca spinal tissue. The Gene-Therapy studies and human experimentation that she was conducting becomes the cause of her loss of funding. It is implied that Grace used a chemical formula that she derived from an Orca whale in the aquarium on herself and that is what caused her to transform into Orca. She is able to easily switch between being Orca and her regular appearance as Dr. Balin. Orca then begins a crime spree in Gotham City by stealing a valuable diamond called the "Flame of Persia" from rouge millionaire Camille Bayden-Smythe. After the theft of the diamond, Batman becomes involved. Orca aims to sell the diamond and use the proceeds to help fund several projects for underprivileged people. After her attempt to sell the diamond back to Camille Baden-Smythe failed, Orca attempts to kill her. Camille's security force shoots Orca several times, mortally wounding her. She begins changing back into Dr. Balin, telling Batman that the only way she could survive is if he gave her the rest of the chemical formula that turned her into Orca. Batman agrees and she drinks the formula. She then reveals that she could never change from her Orca form again and that she will continue her villainous ways. She swims away before Batman could apprehend her. It is revealed that the jewel was then sold to its original owner and that the money was used to build a new recreation center near the aquarium as well as to "...gentrify a derelict waterfront tenement." Following her encounter with Batman, Orca is not seen again until she appears as a prisoner in the Slab during the Joker's "Last Laugh" riots. She is able to escape during the riots with King Shark.

One Year Later: 

Orca is found dead in the sewers under Gotham City. She appears to have been shot in the head by Harvey Dent's gun, although Batman is convinced Dent is not the killer, and her body has been partially eaten by Killer Croc. Orca's husband, Terry, was murdered by The Tally Man while he was being questioned about the disappearance of his wife by Private Investigator Jason Bard. During the investigation it is revealed that Orca was working for The Penguin along with now deceased super-villains KGBeast, Magpie, and The Ventriloquist. Someone had contracted Orca and other super-villains to turn on The Penguin and rob one of his storage facilities. Harvey Dent catches them and instructs them to stay loyal to Penguin and to get any information they could about him. Harvey Dent is the prime suspect in their murders, but it turns out that they were orchestrated by the Great White Shark, who plans on becoming the number one crime boss in Gotham. He manages to kill two birds with one stone, he weakens the Penguin's forces and manages to turn Harvey Dent back into Two-Face.

Powers and Abilities
Orca has enhanced strength and endurance. She is an excellent swimmer and at complete ease in the water. Orca is able to swim under water for long periods without taking a breath.