I’ve been searching through the rulebook for any mention of Eris. It is marked on the solar system map at the front of the book and the universal index says it is mentioned in the Capitol book but I can’t find any information on it. Was fluff for it removed from the game but it was left on the map?
My guess is they planned to use it and then dropped it because of space.
In the universal index, references to Eris in the Capitol book seem to be references to Eos.
Given its proximity to Nero, I would make Eris the home of some weapons (ship maybe), artefact or even seal from the ancients.
I plan to use it to expand some advrentures from the Dark Eden campain, as I find the last part lacking a bit.