Kamerel
If you read up on the lore you might notice that a lot of "breeds" of Outsider in D&D are not the original inhabitants of whatever plane they live on, there having been a race of prior inhabitants who may or may not still be around somewhere and who may or may not have a bone to pick with the current inhabitants. The Baatezu of Baator replaced the Baatorans, the Tanar'ri of The Abyss replaced the Obyrith, and the Yugoloth of Hades replaced the Baernaloth. Each of these original inhabitants is more obscure than the current inhabitants, so it can be forgiven if you didn't know that the themselves-obscure Rilmani of the Outlands kicked out a still-more-obscure race called the Kamerel.
Both the Rilmani and the Kamerel embody the alignment of True Neutrality, but whereas the rilmani embody the "actively seeking a balance" version, the Kamerel embody the "meh" version. But because a race of folks who sit on their asses eating Doritos every day and who have no opinions on literally anything would obviously contribute precisely dick to any DM's adventure, the writers decided to go a different route. Yes, they were isolationists and hermits who didn't interact with the world beyond the Outlands when they ran the place, but there was more to it than that. These fuckers were xenophobes of a degree that manages to make even /pol/ look genuinely reasonable: they actually ignored all evidence that beings other than themselves even existed.
Eventually, one of their number by the name of Hallonac realized that this quasi-solipsism was retarded, but since she was still a living embodiment of apathy, all she did was create a device that copied books from across the multiverse. As long as the book is of sufficient length and the author actually desires that it be read (e.g. no sticky notes, diaries, or personal spellbooks), that device has churned out a copy. This of course resulted in a crapton of books, so she stored them in a giant Library now called Timaresh. Hallonac's kin killed her for this, presumably while calling her a cuck and a race traitor.
They then set up guardians in front of the library and proceeded to ignore the fuck out of it. Eventually, the Rilmani came to be and discovered the Library. The Kamerel, however, would not aknowledge the Rilmani's existence let alone grant them access, so the Rilmani declared war. The Kamerel had no idea how to interact with non-kamerel in any way, war included, so they had their collective ass handed to them and had to flee the Outlands for Stormfront the Plane of Mirrors, of all places, where they reside to this day.
After recovering from being forcibly bluepilled by this near-genocide, they may or may not have created the Nerra to interact with other races for them.