Origin

Wing Commander Sh'ri Valkyr is a Death Cultist from the planet Thanagar.  She discovered Starbreaker's incorporeal essence drifting aimlessly through space.  During the ' Planet Heist' story-arc, the planet Rann appeared to have been utterly decimated.  While tensions were escalating between Rann and Thanagar as a result of previous conflicts, the Thanagarians had a vested interest in discovering the cause of Rann's fiery obliteration.  The secret Cult of the Seven Devils had come across evidence that Rann had actually been teleported away, and replaced with a star going supernova.  Sh'ri Valkyr piloted her ship to Rannian space to see for herself, and wound up rescuing Adam Strange who was also seeking answers about the disappearance of his homeworld.  Seeing an opportunity, Thanagar's High Councillor Thrall orderered that Strange be brought back to their planet to take the fall for Rann's destruction.  Valkyr rescued Adam by teleporting him into her love nest right before he was about to be executed.  She claimed that Thrall's attempt at scapegoating Adam Strange for the disappearance of Rann was merely a short sighted political move, and would cast unnecessary suspicion on Thanagar.  Convinced that Valkyr was telling the truth, Adam Stange continued on with his search for answers.  He used a Zeta-Beam to teleport himself to the Hydra Nebula, the origin of the Rann supernova.  Unbeknownst to Adam, Valkyr had put a tracking device on him in order to discover the location of this suspected new technology.

With the help of the Omega Men, Adam Strange discovered that the new technology was an Omega-Beam based on the Zeta-Beam.  The device was potentially the most powerful weapon ever created as it had the ability to convert astronomical amounts of matter into energy, and could also draw power from the fabric of space/time.  Soon, Adam discovered that it was Sardath that had teleported Rann, and its three suns away in order to keep the Omega Device from falling into Valkyr's hands.  Sardath had to act so quickly that he had no time to inform Adam Strange.  In fact, it was Valkyr's intention to give this technology to Starbreaker.  With it, the Cosmic Vampire would be able to convert the entire universe into energy and beam it into himself.  The rogue Thanagarian Commander was promised to have the honour of ruling at his side.

Death

Not long after Adam had been given the full explanation of what Sardath had accomplished, Valkyr unleashed Starbreaker on one of Rann's three suns.  An epic battle broke out between Starbreaker and an alliance of Darkstars, and Omega Men accompanied by a L.E.G.I.O.N. assault fleet.   Meanwhile, Adam Strange and his allies attempted to return Rann back to normal space with the Omega-Beam, hoping to effectively strand Starbreaker in a dead system.  Aware of the potential threat to her master, Commander Valkyr captured Alanna Strange, and ordered that Sardath power down the Omega Device.  A fight ensued, between Adam, Sardath, and the Thanagarian Death Cultist Warriors.  As Valkyr was attempting to disengage the Omega Beam, Alanna Strange shot her in the back.  However, Valkyr did manage to reprogram the coordinates of the Omega Beam to teleport the Rannian homeworld into the Polaris System, home of Thanagar.  As a result, the Thanagarian planet's atmosphere ignited.  Thanagar crashed into its system's sun.  This was the dawn of the Rann Thanagar War.