The Demon (Dot X)

"When someone sleeps, their mind is at its most susceptible. That's why I needed her asleep to read her mind. The Demon is growing stronger.  Soon it will be able to take full control of her while she's asleep."

- Audrey explaining the demonic possession to Mi "Clone, I can't sleep. I'm thirsty. Please bring me some water."

- The Demon's first comprehensible words The Demon is the primary antagonist of the webcomic Dot X. It was asleep in Time Mountain for millennia before Speedy interrupted Audrey's "Binding of Souls" ritual, which was required to keep the Demon at bay for another thousand years. It may or may not have some ties to the history of Hetrea.

Pre-"Adventure"
Very little is known about its past before the comic. However, it has slept in Time Mountain for millennia, and requires a certain ritual to be performed every 1000 years in order to keep it asleep.

"Adventure"
After Speedy interrupts Audrey's "Binding of Souls" ritual, the Demon emerges from Time Mountain. It forces everybody except for itself, Speedy, and Pudding off of the top of the mountain. It then takes on Pudding's appearance, which Audrey soon explains was part of an attempt to kill and replace her. At some point near the end of this chapter, the Demon enters Pudding's mind.

"The Wonderful"
The Demon makes an appearance near the end of the chapter, playing the role of the Wicked Witch of the East. Beforehand, Frisky (playing the role of the Wicked Witch of the West) warns her that the Wicked Witch of the East doesn't want her to wake up. Pudding and Speedy immediately escape via Speedy's hot-air balloon.

"Night Terror"
Pudding is having trouble sleeping, prompting her brother Mi to take her to his friends Audrey and Danny to help her. Audrey takes Pudding into her bedroom and tells her to fall asleep. Afterwards, she concludes that the Demon has possessed Pudding, and it's waiting for her to be too exhausted to wake up so it can take control of her body. The only option at this point is to keep Pudding from falling asleep.

"The Ball"
Mi has accompanied Pudding to the titular ball in order to monitor her. Meanwhile, Pudding is attempting to stay awake during the party in order to prevent the Demon from taking over, causing her friends and fellow party-goers to be concerned for her. Eventually, Mi tells Speedy to enter Frisky's castle disguised as Frisky's boyfriend, Fade, in order to keep an eye on Pudding. Speedy is eventually found out by Frisky, and he warns her and Clone that Pudding is possessed by a demon. However, by the time he does this, the Demon has already taken over Pudding's body.

Trivia

 * The Demon has also appeared in the now non-canon video game Dot X Adventure, in which it served as the final boss.
 * According to the webcomic's creator, the Demon is a Monster, which means that it spawned (much like an enemy in a video game) somewhere on Hetrea, and if it dies, it will cease to exist.
 * Although Dot X contains both angels and demons, the Hetrean versions of these creatures have no relation.