The Invisible fiend was a fiend featured in episode 13 of the Making Fiends web series. It was made by Vendetta to cause general chaos and to destroy Charlotte. Vendetta kept it in a cage until it was sent upon Charlotte.
It was seen to be very strong as it was able to break through the bars of the cage and throw Marvin across the playground. Vendetta also described it having pointy teeth. This fiend eventually met its demise when Charlotte impaled it with a kebab. It was not invisible when it was made, and was made invisible with an Invisible drink made by Vendetta. This invisible drink was drunk by Charlotte after she killed the Invisible fiend. Charlotte mistook the Invisible Fiend as Vendetta's imaginary friend, mentioning her imaginary friend Carl.