It's interesting that in the MK4 comic, "Edenia" actually had the shokans and centaurs in it too. So, it was basically "Outworld", but they named it Edenia in the comic or maybe Sindel, replacing Shao Kahn, just decided to change its name.
And I think a very good question arises: why did Shinnok chose Edenia/Outworld to enter the living realms? Why not open a portal to Earthrealm? Or to Seido? Or to Chaosrealm? We know from the MKX story mode that every realm has a Jinsei and its power is so great that it could enhance Shinnok very much and give him the power to battle the Elder Gods.
In my opinion, Shinnok chose Outworld in order to get to the Jinsei there. Outworld was now weakened after Shao Kahn had been defeated and Sindel was just not strong enough to keep Shinnok out. Outworld was also a very powerful realm, combined by many realms: Edenia, the realm of the shokans, that of the centaurs, of the tarkata etc. So, absorbing the Jinsei there made Shinnok probably powerful enough to climb to the Heavens and defeat all those Gods that we learn of in the MK4 story.
