* Fan-made project: Many fans create their own stories, animations, or games in the Sonic universe. If you're thinking of a specific project, please provide more information about it, like where you saw it or what kind of media it is.
* Misremembered title: It's possible you're remembering the title incorrectly. Perhaps it's a different Sonic game or piece of media?
* Unreleased project: It's possible this is an unreleased project or concept that has not been officially announced.
Please provide more context so I can help you figure out what "Sonic Epilogue" refers to.