|First Appearance||Trouble in the Yard|
The demon first appeared in the early days of the North Western Railway, possessing Timothy with the intent of plunging Timothy and his passengers into a ravine. However, its plans are failed. When the crew uncoupled the train, They send Timothy plunging into the ravine.
The spirit went unseen for many years, when it returned by influencing Diesel. However, shortly later the demon enters Duck when he pushes Diesel over a broken bridge. From this point forward, the demon uses Duck to systematically target all the diesels of Sodor. After all the diesels experience accidents related to Duck, they band together to detain him for his actions. However, Thomas and Percy have come to the conclusion that Duck is not responsible, and solicit the help of Toby to exorcise the demon. However, Toby fails to exorcise the demon, allowing Duck to escape.
Thomas, Percy and the diesels, now with the help of Edward, they set a trap for Duck using Rusty as bait the following night. They surround Duck and manage to successfully exorcise the demon from Duck, instead transferring it to S.C. Ruffey. From this point forward, the demon vows revenge on all the engines of Sodor.
While in S.C. Ruffey, the demon continues to cause trouble by using his new form to push Edward down Gordon's Hill, causing a crash at Knapford Station. Later, S.C. Ruffey was placed on Henry's night goods. As Henry and the trucks set off, they encounter the Slender Engine, who preys on Henry and absorbs the demon in the process. The Slender Engine uses the demon to increase its power, preying upon and eliminating many of the engines on Sodor. Before he can finish off Thomas and Percy, it is apprehended by the Halloween Engine .
The demon is a force of evil intent on upsetting order on Sodor. It manifests it power through possessing various engines and rolling stock, using them to complete its schemes. When in control, its host has glowing red eyes, a rather evil laugh and a deep demonic voice.
- Trouble in the Yard (Diesel, then Duck)
- Branchline Diesels, Mainline Trains (Duck)
- Dirty Diesels (Duck)
- Diesels, Ducks & Demons (Duck, then S.C. Ruffey)
- Troublesome Trucks (S.C. Ruffey)
- Trick or Treat (S.C. Ruffey, the Slender Engine)
- The Tedious Tale of Timothy (Timothy)