The Demon Guard appears in "Return to the Nightosphere." He runs the prison in the Nightosphere. In the episode he lets the prisoners out when his shift is over because no one shows up to take his place. He justifies this by pointing out that that they're still stuck in the Nightosphere so they aren't really free. He fills the cell that Finn and Jake are put in with "the stuff," or the banana-like things that come out of his ears.
The Demon Guard is a bat-like demon. He has two horn-like ears and a very similar horn-like structure pointing downward on his chin. He has bat-like wings attached to his arms. His body is completely red with 2 goat-like legs. He is normally seen in possession of twin cutlasses. He also wears a harness that supports his two cutlass sheathes.
- In the line to speak to Marceline (while she looks like her father) and during the Political Rap song there where multiple other demons of similar apperences, implying that he is not the only demon of the subspecies.
- His eyes appear to glow in dimly lit areas, such as the prison, but go back to normal when he turns the lights on. They can glow red and neon green.