....Technically this is less of an Isekai, and more of several AUs in a Trench Coat that's managed to clip themselves into the backrooms by sneezing too hard.
Originally an idea for a fangame, and drawing from almost every bit of Sonic media possible, [The Mainline Games/IDW Comics, and One April Fools Game in particular,] Galaxy Spiral is a fun little writing exercise taking a bunch of non-canon bad ends, unused plot elements, decanonized games and events and a couple of "what ifs" that amused the writer enough to put in a blender and puree.
Less of a specific Sonic Thing and more of just "The Vibe"
Originally an idea for a fangame, and drawing from almost every bit of Sonic media possible, [The Mainline Games/IDW Comics, and One April Fools Game in particular,] Galaxy Spiral is a fun little writing exercise taking a bunch of non-canon bad ends, unused plot elements, decanonized games and events and a couple of "what ifs" that amused the writer enough to put in a blender and puree.
Less of a specific Sonic Thing and more of just "The Vibe"