The Devil Watcher is a creature that appears in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. According to Knuckles, the creatures appear exclusively in Mobian fairy tales.
Knuckles encountered one Devil Watcher on his way through a remote section of the Great Forest on his quest to find the King's Sword of Acorns, causing him to remark upon its status as a creature of myth, before causing a tree to fall onto it. This caused it to apparently "die", dissolving into a grayish mist.
Merlin Prower later revealed that the Watcher had been summoned by himself as one of the ways he protects himself as a charlatan.