You know the story. A white character is in distress. Not immediate, potentially fatal distress but more like a personal crisis. Then, all of a sudden, a black or Indigenous person shows up, knows exactly what clever things to say and do. She fixes everything, then disappears into thin air (literally). The End.
"The Magical Negro," a phrase made famous by Spike Lee and "The Noble Savage" are essentially side-kick characters included in a story to create the allusion of diversity, a token. There are some serious problems with this trope.
1. The character only exists in the world and sometimes quite literally, only in the presence of the white character. It references a time in real life when blacks were solely around to serve white people. As if they didn't have their own lives, stories, or histories.
2. It's one dimensional. The character never changes and has no arc. To be frank, it's boring.
Sci-fi and fantasy writers you have to be extra careful of this as some of your characters may actually be magic. You'll want to make sure your non-white magical character is not there only to save the white protagonist.
I added the "& Friends" to the title of this post because we don't see this in just black characters. It's often a trope found in Indigenous American characters known as "The Noble Savage." A character who is wild and close to nature but ultimately good and loyal and like The Magical Negro, completely dedicated to aiding the white hero. Often times the character will have some vague magical abilities that are derived from nature, a connection left unexplored.
Zoë Wasburne, from the amazing space opera, Firefly (if you don't know it please do yourself a favor and watch ASAP) is a great example of a "save the day" non-white character that isn't a trope. She's loyal, she's badass, she has history, and she is her own person separate from the Captain Malcolm Reynolds. She has a life and a family and we get glimpses into that. She has a personality! Her ability to "save the day" doesn't come from some ambiguous magical skill or being in-tune with nature. She's a fighter. She's skilled and trained. One thing I love about how Firefly writes her is she gets challenged. People call her out on her seemingly blind loyalty and she explains herself.
Your side-kick characters needs a story, a community, and a purpose. The reader doesn't need to know all of it but the reader should know something about the side-kick that is outside the world of the hero. See my services page if you'd like to be in touch with me about this more in your own story but the most succinct advice I can give is: give your character a life.