The Lady Sybil is a member of the Imperial Guard, a multi-ethnic group of super-powered alien beings who act as enforcers of the laws of the Shi'ar Empire. As Oracle, she was amongst the first of the Imperial Guard encountered by the team of superhuman mutant adventurers known as the X-Men who sought to rescue the Princess-Majestrix Lilandra from her insane brother, then-Majestor D'Ken. Following the orders of their emperor, the Guard clashed with the X-Men and were on the verge of winning when the band of interstellar freebooters known as the Starjammers arrived to turn the tide of battle in the X-Men's favor.
The Guard and the X-Men subsequently clashed once more when the Shi'ar sought to end the threat to the universe posed by the cosmic entity known as the Phoenix, which had assumed the form of X-Men member Jean Grey. As the Guard's only telepathic member at the time, Oracle was an obvious choice to be one of eight Guardsmen chosen to battle the X-Men. The Guard defeated the X-Men on this occasion, but the mutants were allowed to return to Earth after Phoenix seemingly committed suicide.
Soon after, Oracle was amongst those few Imperial Guard members who opposed the treacherous Shi'ar High Council member Lord Samédàr who was aiding an attempted coup of the Shi'ar throne by Deathbird. Even after many of the Guard chose to side with Samédàr, Oracle remained steadfast in her loyalty to then-Empress Lilandra.
Later, after the formerly-exiled Deathbird had usurped the Shi'ar throne, Oracle was amongst those Imperial Guard members who clashed with the British team of costumed adventurers known as Excalibur and the Starjammers over the fate of the then-bearer of the cosmic Phoenix Force, the alternate future daughter of the X-Man Jean Grey named Rachel Summers.
Much later, the intergalactic teleporter Lila Cheney transported the X-Men to the Shi'ar Empire at the behest of then-Empress Deathbird in time to see Lilandra regain her throne. Not all was as it seemed, however, as in reality a group of Warskrulls, using technology to allow them to duplicate superpowers, had captured and impersonated the X-Men's founder, the telepathic Professor Charles Xavier, using his telepathy to control Lilandra and the Imperial Guard including Oracle, whose own telepathic powers were no match for Xavier's. After the ruse was discovered by the X-Men and all the Warskrull impostors were exposed, Lilandra settled matters with Deathbird, discovering her sister did not want the throne anymore.
During the war between the Shi'ar and Kree Empires, Oracle was part of a small team of Guardsmen who were charged with discovering the whereabouts of the powerful Kree weapon known as the Omni-Wave Projector. Oracle's team captured the Earthling named Rick Jones, a long-time ally of the former Kree soldier known as Captain Mar-vell, and learned of the location of the device by scanning Jones' mind.
When the Empress Lilandra, having regained her throne, learned of the many Earth heroes that had sacrificed their lives to stop the malevolent psionic being named Onslaught, she dispatched eight members of the Imperial Guard, including Oracle, to protect Earth. While on Earth, the Guard uncovered a plot by a militant Kree faction to simulate a radical political activist group in revenge for Earth's involvement in the Kree/Shi'ar war. In reality, the group created a "nega-reactor", similar to the bomb that was used on the Kree. However, this plot was stopped by the Guard, but not before the reactor was used by the Kree's leader, the Supreme Intelligence, to re-incorporate itself after being presumably killed at the end of the war.
During their brief stay on Earth, Oracle and her fellow Guardsman Gladiator learned that a fugitive from Shi'ar justice was hiding on the planet, stuck in the form of a child and with no memory of his former life. Their search brought them into confrontation with the gamma-spawned man-beast known as the incredible Hulk.
In her time as a member of the Imperial Guard, Oracle and her fellow Guardsman Flashfire had fallen in love and planned to marry. She took the opportunity to retire from active duty with the Guard, and her place was taken by the telepath named Delphos.
For reasons unknown, Oracle's relationship with Flashfire did not last, and she later returned as a member of the Imperial Guard following the mental possession of their Empress Lilandra by Charles Xavier's mutant twin sister Cassandra Nova and her decree that all mutants on Earth had to be destroyed, starting with the X-Men. Oracle's appearance had changed drastically - instead of the refined, well-kept woman she once was, Oracle now appears as a naked, feral harridan. During the ensuing clash, Oracle was defeated by the group of young telepaths known as the Stepford Cuckoos, whose combined mental abilities proved more powerful than Oracle's own.