Eve thought she was alone in the universe. She wasn't.
Thelarians had her genes. They had been experimenting. Their efforts did lead to something. The result was however... unkind. unstable. The result was...
...Sable.
She was stronger than Eve. Her growth was guided. She discovered her xenomorphesis much sooner and unlike Eve, she was born a woman, not a child.
The excessive genetic tempering by Zaalthore however had left its mark. Sable's face had a grotesque defect. No lips and cheeks, visible teeth. She despised it. It looked ugly and she hated it. Zaalthore promised her a cure using Eve's DNA. Sable agreed.
She was fierce, ferocious, merciless. Thousands of Thelarians died at her hand before she calmed. Dr. Zaalthore cleverly tamed her.
"Kill all the Thelarians you want. Kill me as well. But I won't abandon you like Kyle abandoned Eve. Sable, you are precious, valued. You have all her gifts, without her human flaws. She was just a decoy, you are the ultimate, the future..."
Dr. Zaalthore convinced her she was one of them.
Thelarian high authorities made her a high ranking officer equivalent to Eve. Gave her a spaceship, an army and all the clearance to do whatever she wants. Soon, her ruthlessness was feared even within the Thelarians.
It all manifested when multiple Intergalactic Committee outposts and spaceships were destroyed in a short time. Witnesses reported something that would otherwise describe Eve. But she was publically stationed on Nomad all this time.
Sable inflicted the IC more blows within weeks than they had suffered in years. What's worse? Thelarians were expanding their operations.
Amidst the chaos, Amorfati incident happened in which Eve's squad was badly defeated in a clash with Thelarian's new supersoldier.
Under Sable's flagship, Thelarians had established an outpost on a planet on the outer edge of the Dark Galaxy. They never stepped out so far out from The Eclipse Corridor, where they had been hiding all this time, behind the cover of dangerous creatures.
From that planet, now recognized as Sceptor One, it didn't take long for Thelarians to extend their roots to Amorfati. Several IC space commanders attackes Sceptor One with full force, but a new faceless power had turned the tables. The IC didn't have a name for her at the time. They just called her The Phantom.
Thelarians, who lived in hiding, now came out in the open. The IC commandships for the first time in centuries were on the run from the Thelarians.
Eve eventually took a trip to Amorfati and defeated Sable. Surviving Thelarians abandoned the outpost and fled back to Sceptor One. But events at Tenhunny had exposed a darker truth: Thelarians were harnessing the power of monoliths. And Sable... was not only alive, she had become invincible.
Using monoliths powers, Zaalthore had somehow found a way to transfer Sable's consciousness to a newly printed body after her death. And it was cyclic, reproducible. A technology perfected.
Nomad had passed on the intel to the IC's ruling members after Tenhunny's president was assassinated. Sable: The Phantom, was now everywhere in commander's logs. Eve's team was now more concerned about monoliths and Sable's emerging role on the intergalactic stage of power.
Sable's misadventures continued to create obstacles for Eve and her team. Sabotaging her missions, disrupting her plans. In every sense, Sable had become Eve's perfect archenemy.