That's just what she's known as.

Y/C finds themselves on some space station or some shit, far from their homeworld. Interdimensional travel through those weird green portals is a luxury, so for now, you've just got some pre-owned spaceship. And through your interstellar travels, sooner or later, you cross paths with Cassandra. And she could absolutely tear you apart.

(Very general scenarios for you to interact with her and get things rolling)