Now my short story has been well and truly torn to pieces (I am very thankful to everyone who managed to read the 'story') I need to try and make something out of it. Many of the points I am fixing on my own, some others with help but one point I really don't know how to fix. The world which my characters inhabit is full of fantasy races, some known, others of my own invention. I have modified imps who cause illusions, zoomorphs who are werewolves but for every animal and ralacees who have heated areas of skin. My question is how do I introduce a new fantasy race to readers? The characters can't be used as a vehicle to introduce this (I do find it annoying when new people are added just to explain things) as they already know everything about these races, so how do I do this? Thanks!
You can just have them appear in the story when they appear, act as they act, and so on, without any explanation of the race to the reader. The reader can then gather information over the course of the story. See, for example Steven Erikson. That certainly eliminates the problem of characters or devices that exist simply to tell the reader something.
Put the characters in a situation in which they would be forced to utilize some aspect of their race. Have an MC get tricked by an imp's illusion for example. If there isn't a need for the reader to know that a race can do something maybe don't force it until it comes up naturally in the plot, while you have a cool race invented in your head it could come off as awkward and forced if someone is blurting out features of the race etc. with no context (it would be a thin guise over the fact that you want to introduce a race). Also I don't see anything wrong with dropping narrative hints about the differences in the races or just talking about the characters reacting to the world. If a character is 3 feet tall he is going to perform different actions versus full size characters, versus if a character is extremely nimble and agile you will see him utilizing his skills while other characters can't (I'm thinking about how much I learned about Elf's in LoTR just through Legolas being utilized by the group to perform tasks that the rest could not, I never even stopped to think I was learning about elfs, it just came naturally with the narrative). But I totally agree introducing new dumb characters for the sake of having others need to explain things to them seems like a transparent trick. Hope that made some sense... I'm a fantasy writer as well but never utilize other races or at least haven't yet so this was kind of fun for me to think about, let us know how it turns out.
It also removes a serious breach of POV. If your characters know who and what these people are, having them (or some other device) explain is out of sync with their world. It would be like me explaining to @Steerpike what a Latino is. He might humor me for a bit, wondering if this information is going somewhere new, but when it doesn't from his perspective, he's going to tell me, "Uh, dude, I'm from California. I know what Latinos are." He might also squint to check if my pupils show signs of substance abuse. Have your characters deal with the new race the way that would be most normal to them, to their engagement.