The Kryptonian Science Council discovered that two of their most revered scientists, Jor-El and Non, had determined that in a short matter of time, Krypton would suffer geothermic upheavel that would destroy the entire planet.
Branding them as heretics, the cowardly members of the Science Council sent General Zod and his militants to Jor-El's laboratory to arrest he and Non. Ursa was in charge of placing the two scientists under arrest and handing them over to the council. The Science Council administered a stern warning to them, and set them free.
Before long, Zod and Ursa discovered that Jor-El and Non had been right all along. Krypton had little time left. Non ignored the Council's warning and preached to the populace of Krypton revealing everything he knew of the pending disaster. Zod and Ursa defected from the military and joined Non's cause. Soon after, Non was captured and lobotomized under orders of the Science Council.
This incident drove Zod over the edge, and Ursa and he began an insurrection that made them the most wanted criminals on the planet. They were eventually captured and brought to justice. Jor-El argued on their behalf, and swayed the Science Council from sentencing them to death. Instead, Jor-El elected for a more peaceful means of punishment - exile in the Phantom Zone.
Ursa, Non and Zod remained in the Phantom Zone for many years. During this time, Zod and she mated and produced a son, Lor-Zod. Their child eventually escaped from the Phantom Zone and arrived on the planet Earth. He came under the care of the last surviving Kryptonian, the Son of Jor-El, Superman.
Shortly after this event, Ursa and the others broke free of their confinement and journeyed to Earth to reclaim the Kryptonian child. They attacked the city of Metropolis and Ursa raided the offices of the Daily Planet where she found Lor-Zod in the care of Lois Lane. Cornering her in a stairwell, Ursa incapacitated Lois with a simple flick from her index finger.
She then took her son and returned to Zod, taking Lois along as a captive. She stood by his side as he interrogated Lois, stating she didn't understand what made Kal choose that particular female. She was as suprised as Zod when Lor used his powers to defy them and protect Lois. They were even more suprised when a returned Kal-El fought them alongside Lex Luthor and his allies.
They were defeated and returned to the Phantom Zone. They would be in the Zone for a just a few months before the events surrounding the liberation of Kandor took place. In the end, Allura chose to free and pardon her along with Zod and the rest of his followers in the Zone. They were placed in control of the Kryptonian Millitary once more, on the New planet Krypton.