While Oracle serves as the basic head of operations, Black Canary becomes her full-time employee and field agent. In 2000, the first Batgirl monthly comic was launched with Cassandra Cain as the title character. Oracle appears as a supporting character throughout the series, acting as a mentor to the new Batgirl, alongside Batman. Gail Simone took over as writer of Birds of Prey with issue #56. In an interview, Simone explained her fondness for Barbara Gordon, stating: "Kim Yale and John Ostrander picked up the character and made her into a brilliant master computer operator and one of the most fascinating characters in comics. From there, Chuck Dixon did wonderful things with her in his Birds of Prey run ... She's fantastic because even just sitting in a chair in a dark room by herself, she's tremendously compelling. The DCU without her would be a much less interesting place." Simone integrates the Huntress into the comic, making her a central character in the series as Oracle's secondary field agent. In 2003, comic book authors Scott Beatty and Chuck Dixon revised Barbara Gordon's origin with the miniseries Batgirl: Year One. Gordon is a highly gifted child having graduated from high school early, but initially desires to join law enforcement as opposed to vigilantism in the previous origin myths. During the 2004 crossover event Batman: War Games, Black Mask commandeers Oracle's computers and satellites and engages in a fight to the death with Batman. To prevent Batman from killing his adversary, Oracle initiates the Clock Tower's self-destruct sequence, provoking Batman to rescue her rather than continue the battle. This destroys Gordon's home and headquarters in the clock tower. Subsequently, Oracle decides to move on and leaves Gotham City altogether. She cuts her ties with Batman, and after a temporary world trip with her team, relocates to Metropolis. In the events comprising Gail Simone's Birds of Prey: Between Dark and Dawn (2005), and Birds of Prey: The Battle Within (2005), Oracle is possessed by arch-villain Brainiac, an artificial intelligence entity, in order to become a biological being. Although Oracle overpowers Brainiac and expels him from her body, the advanced virus delivered by him remains despite his absence. The virus steadily causes cybernetic attachments to sprout all over her body. Oracle develops supernatural abilities that allow her to psychically interact with computer information systems. Although she loses these abilities after the virus is rendered