‘Unknown’ is the voice that main character in Slipdrift communicates with for a majority of his time in prison.  The subject has clearly advanced ICS technology as he can not get any read on the voice, nor does it have any visible avatar.  ‘Unknown’ is short and somewhat mean to ‘Yourself’ and he wonders how the voice got his ICS number.

As the story progresses it is clear the voice is orchestrating a potential escape involving both the main character and another Solarian who is never named but described by his Sword tattoo on his cheek.  Through the voice’s intervention the resolution of the story is brought about.

Spoilers for Slipdrift:

‘Unknown’ is the Aelisha receptionist that is met early in the story.  She injects a ICS override into ‘Yourself’ when she scratches him.  ‘Sword’ also shows a deep cut on his arm from where she did the same to him.  She is an Aelisha agent sent to help bring down illegal slave rings.

She saves the two of them at the end as they dive for her cloaked ship and leave the planet.