There are no longer any active military or research campaigns in the Eris region – it is overrun. Long evacuated Corpus and Grineer vessels drift aimlessly in orbit, slowly being devoured by the techno-organic parasite known as the “Infestation”. What remains is a twisted graveyard of partially-digested ships that are disfigured versions of their original forms... Abandoned, but not unoccupied.
Eris also has the unique distinction of having two unique Assassination targets: Mutalist Alad V and the Jordas Golem, each occupying their own nodes and having their own unique missions. While Phobos was the first planet to have two Assassination targets with the team-up of Captain Vor and Lech Kril, unlike with Eris both bosses are found on the same mission, and the pair are considered a single Assassination target.
Interestingly, as Mutalist Alad V requires a key to access, and "The Jordas Golem Assassination" has the Jordas Precept as a prerequisite, unless the player has the components for Mutalist Alad V's key or the Jordas precept quest completed, there are no available assassination missions available on Eris.
The two individual boss-fights on Eris make it the first planet in the game on which two Warframes are dropped.
Prior to Update 11.0, Eris's (and Europa's) description read: "The Infested are spreading throughout the Orokin Derelicts in this region". This implied that at least some of the Orokin Derelicts are located here.