The Infernal Plane

"COLIN: Demons?""FAENDYR: They live in another dimension, like faeries, only... they're meaner.""COLIN: Meaner than faeries?! Oooooh."

About
The Infernal Plane is one of the four known Planes of Existence. While little is known about it in the Mortal Plane, it is most notable as the home plane of the beings known as Demons.

Residents of the Mortal Plane are unable to travel to it, because it exists in fourth-deminsional space. It is unknown if the Fae are able to do so.

Demons
Despite the popular idea, demons are not inherently bad. This reputation comes from the fact that as inter-deminsional and (presumably, according to them) immortal, they often have a disregard for the well-being of "lesser" beings. They often liken it to human and elves' lack of regard for insects' lives.

The true appearance of demons is an issue of debate in the Mages' College. Because mortals cannot behold their true form, they always appear to mortals in a guise they are able to comprehend.

Quotes

 * "The ways of the demons are complex. We make our plans on the scale of millennia. Your measly three- dimensional brain could not possibly grasp our motivations." Snowball, Episode 5

Trivia

 * It is often used as a mild expletive (ex: "What in the Infernal Plane?")