Most likely just a coincidence.
Iirc, then eternum is supposed to be a futuristic skin line with aliens that are corrupting lifeforms.
Basically they are the Borg, metal based alien race that is assimilating other life forms to serve in their collective.
And Cassiopeia is most likely supposed to be the queen, one of her animations even shows her corrupting a ratlike creature.
In her splash, you see that she seems to be in a place with high technology, most likely a spaceship.
Darkin, as far as we know, are not working like that. Sure, they are able to take over someone's body and inhabit it themselves. But they don't corrupt living beings to become one of them without taking its place.