Devil Squidward is the fictional embodiment of Squidward's bad moral compass. He only appears in the episode "Sportz?"
He has a similar form to Squidward, except he wears a long red robe which is torn at the ends, and four sandals, one on each foot. He also has a pair of red horns, a red pointed tail, and a pair of black bat-like wings, which look like they are attached to his body via shoulder straps.
He seems to be sadistic in nature, as seen when he tells Squidward to purposely misteach SpongeBob and Patrick how to play sports.
After Angel Squidward warns Squidward that incorrectly played spots can be dangerous, Devil Squidward appears and agrees with Angel Squidward, telling Squidward that he should get SpongeBob and Patrick hurt by having them continue playing sports incorrectly.
His wings are apparently fake, as they seem to be strapped to his body.
His wings are never shown flapping, leaning towards the fact they may be fake.