This universe has a civilization of humans! And some other things. It's not crowded in the way Edda is but it's not just the one planet either. The humans might be easiest to start with. They're on that planet over there, it's not Earth but it has very Earthlike conditions and bronze-age humans living in cities and villages dotted across two large continents. Depending on how thoroughly any prospective visitors look they might find other things before visiting.
It's really hard to explain! Feeling is far more critical than thinking for matters of the spirit. Here is how splitting feels (bounce: Dozens of sparks of always-present joy and comfort in the dark, echoing the same feelings back in cycles, even when one vanishes none have really vanished; Hard-long-desperate-tired-learned-fear warring with opportunity-curiosity-wonder-awe; A sense of mounting tension, then- Like the sudden departure of a dance partner, sudden nothingness, freedom and loneliness bittersweet.)
The rats are perhaps surprisingly clean and sanitation-conscious. It helps keep down on disease. They're very curious about this new place, carefully exploring it and asking their friendly escort elf all sorts of questions. Where is her family? What does one even do when food and safety and ensuring future food and safety aren't immediate, overriding concerns? Besides learn to read, which they are gamely attempting.
This Elf is not married; her sister and brother-and-law live next door, and her parents live the next town over. She's in osanwë range of all of them, osanwë between Elves might reach father than whatever holds the rats together. She likes to sing and play the piano and go on hikes and ice skate and, yes, also read, when she isn't working.
Music is... Strange, but not unpleasant. They are very motivated about how so many secrets lie behind the veil of reading and are trying very very hard about it. They have better luck parallelizing long passages rather than reading a single word at a time.
They understand family more than any of those other hobbies, and would be delighted to meet hers.
As long as he gets a bit more gentle after a small warning squeak, more rats will come be petted a few at a time sniffing at his hands and clothes, including the little-kid-rats whose fur is very short and soft, bodies just two or three inches long including tail.
Your family is not as close as our family, we are one and many and almost all the same. What is it like?