The Interstellar Concordium is mainly native to Node 23 and it's alts. However it can reoccur in other places.
It is a group of more than 200 planets and 60 native species. on the surface, they look a lot like how the United Federation of Planets bills itself. However, they have two major differences.
1 - the ISC is pacifist above all, ironically, they love peace so much, they'll go to war to prevent other people from making war. Many natives of the ISC are fully aware of the cruel Irony here. Many drink about it. Others make rationalizations to the effect that the Final War (Or,as it's officially called, the Pacification Campaign) must be ended with the conquest of the outsiders to protect the Final Peace, the sooner victory is achieved, the more lives can be saved and the more peace can be had.
2 - The ISC has no respect for cultural rights or individual rights. Their social order is enforced by telepaths who think nothing of mentally altering criminals and rebels in such a way as to play nice with others. They have run roughshod over non telepathic species in order to achieve the peace they crave,
The core races founding the ISC
Veltressai: Humanoids with bald, double lobed heads, the Veltressai are the core of the ISC. They are a telepathic species, related to humans. Their culture resembles the Zhodani from Traveller. "Be nice or we'll make you be nice" would be their motto, if they were being gauche about it. In normal times, they form a cadre of "Political officers", psionic enforces and mind-hackers who keep the other species of the ISC in line and happy. Opposition to their rule is considered insane and dangerous inside the ISC, They view the rest of the Galaxy as Mad Max with Blasters.
Korlivilar: A felinoid species.
Pronhoulite: A reptilian species
Q'naabian: From a cold planet with an atmosphere of chlorine, the Q'naabians are the technicians of the ISC.
Rovillian: Intelligent dolphins with a mild telekinetic ability who, incredibly, built starships and explored space.
Node 23 Prime - In this alt, the Veltrssai
In this Alternate, the ISC has just been founded by Veltressai, who were contacted by the Rovillians.
This is based on the Star Fleet Universe, and so deaults to that unless specified different.
Note that This node like all the others in this string defaults to Star Wars Style super science and so this node features the races of the SFB universe, armed with the technology of the Star Wars Universe - so. Yeah. Like that.