Nisja

Nisja of Titan was the primary antagonist of the second Orphans of Mars book, To Bell The Cat.

Before the Genetics War
While the Titanians were wiped out, and their planet ruined, in a war with Mars some thousand years before the Martian Genetics War, Nisja survived as a bounty hunter for the Pulse Collective in Deep Space, thrown into cryogenic sleep between jobs.

When, over a thousand years later, Nisja learned of her planet's fate, she swore vengeance upon the Daughters of Mars, who had carried out the genocide. She arrived on Mars to find it already destroyed by the Genetics War and the iron oxide bomb. She apparently destroyed what remained of the White City and its inhabitants before setting her sights on Earth.

To Bell The Cat
Nisja's ship crashed on Earth, fatally compromising her life support systems. With only days or hours left to live, she began looking for the Daughters of Earth Colony.

She ran afoul of the assassin Danalee, and they fought an indecisive duel inside the wreck of the Cydonian ship. The Twain then began to hunt after Nisja.

She escaped them, coming across their Imperatrix, Nerrine, near the sea. She was about to kill Nerrine when the old rex snatched her up in her jaws, ending her life.