Diesel 10 is an evil BR Class 42 "Warship" Diesel with a roof-top, hydraulic claw named "Pinchy" and the main antagonist in Pooh's Adventures of Thomas and the Magic Railroad. He and The Grand Duke of Owls tried to destory Lady the Lost Engine, seeing that steam engines are untrustworthy to today's standard's or railway industry. but Thomas, Lady, Burnett, Pooh and his friends managed to defeat them by making them falling of the viaduct and into a barge of slundge.
Diesel 10 had been to Sodor a long time ago, creating problems for the steam engines. He chased down Lady - the engine who kept Sodor alive - and made her crash. In the years that followed, Lady's caretaker, Burnett Stone, took her into hiding, trying desperately, but failing to bring her back up to steam.
Diesel 10 returned many years later, intending to destroy Lady for good. He brought with him two lapdogs, Splatter and Dodge, who were present when the boss was scheming. He was first seen in the movie charging past Thomas and Gordon at Maithwaite. He also dumped sneezing powder all around Tidmouth Sheds so that the wind from Harold's blades would blow it all over the place. Diesel 10 had very little success with his plans - Mr. Conductor caused Pinchy to throw him safely onto bags of flour, and during a speech on "how to stop being stupid", he caused a coal chute to empty its contents on top of him at The Coaling Plant.
By using special coal from Sodor, Burnett Stone was able to bring Lady back to life. Diesel 10 was determined to attack her, but lost the aid of Splatter and Dodge. Burnett, Lady, and Thomas found themselves being chased by Diesel 10 over an unsafe viaduct. The center of the viaduct collapsed, and while Thomas and Lady were able to cross safely, Diesel 10 was too large and fell into a passing barge below.
How Diesel 10 got back to Sodor is a mystery. It is likely that Sir Topham Hatt decided to give him another chance.
Thomas and Mavis went to tell steam engines and Diesels all over the island to meet at the coaling plant, a chance and hope for them to work together and get the new Sodor Airport built on time. When Thomas went over to tell Diesel 10 about the meeting, he got scared to his wheels. Not sure if Diesel 10 would want to help the steam engines anyway, due to their difficulties in the past, Thomas sped away as fast as he could.
Construction of the airport was almost complete when a tower collapsed, cracking the runway and blocking the tracks. With Harvey too far away to clear the line, Thomas took a chance and decided to ask Diesel 10. Convincing his former archenemy that helping the other engines would prove how useful he was, Thomas returned with help to clear the line.
At the end of Misty Island Rescue, unbeknownst to the steam engines, Diesel 10 was seen on a bridge overlooking the Sodor Search and Rescue Centre threatening them.
In Day of the Diesels, he later tricked a lonely Percy into helping him take over the Sodor Steamworks. When Percy had a falling-out with Thomas, Diesel 10 used him to attempt to have the Sodor Dieselworks repaired. After convincing Thomas to go to the Dieselworks, Diesel 10 had Percy lead him and the other Diesels to the Steamworks. When they arrived, Diesel 10 betrayed Percy and took over the Steamworks. He retained the comedic humour that could be seen in Thomas and the Magic Railroad; for example, when he rolls back into his shed, the doors close on him too early, leaving him stuck for a few seconds before goes all the way back into the shed and the doors close completely.
When Percy went to the Dieselworks to rescue Thomas, Percy saw that sparks from "Pinchy" had set the main shed ablaze. After saving Thomas and putting out the fire, Percy led the steam engines to the Steamworks. After a brief argument between the engines, the Fat Controller arrived. Percy told him that the Diesels needed a new Dieselworks, so the Fat Controller had the steam engines and Diesels work together to rebuild it.
Diesel 10 is now in charge of the Dieselworks, but Den and Dart run it when he is not around.
In the seventeenth season, Diesel 10 was stealing Christmas decorations from the Steam Team at Tidmouth Sheds with Paxton's help because he thought no one liked diesels. That afternoon, Percy caught him stealing the last of the decorations and bravely raced after the evil diesel in an attempt to get the decorations back, enlisting Edward, Thomas, James, Henry, Gordon, Toby, and Emily to help him. After taking back the decorations, Paxton told Diesel 10 that Sir Topham Hatt gave them a truckload of decorations for the Dieselworks. At the end, he decided to give the Steamies back the decorations, though most of them were crushed by Pinchy, so to compensate, he gave them the diesels' decorations because they considered Sidney to be a good enough decoration.
Diesel 10 is an evil, conniving, bullying, and psychotic monster. He absolutely despises steam engines, and would call them taunting names like "puffball" and "teapot". He is Sodor's strongest but not quite largest Diesel, his power being enforced by his slightly malfunctioning claw, Pinchy. He can use this deftly, and is even able to use it to make a sculpture. All engines, steam and diesel alike, fear and respect him.
Despite his aggressiveness, he will help on occasion since Sir Topham Hatt brought him back, but only when it suits his personal interest. He can have a caring side, but he very rarely shows it.
- Diesel 10 will become Ash Ketchum, Littlefoot, Simba and Tai's enemy in Ash's Adventures of Thomas and the Magic Railroad.
- Diesel 10 will get his revenge on Pooh, Ash and Thomas in Pooh's Adventures of The Elm-Chanted Forest, but will reformed later after Pooh's Adventures of Thomas & Friends: Day of the Diesels.
- Diesel 10 will become Tino Tonitini's enemy in Weekenders Adventures of Thomas and the Magic Railroad. And he'll get his revenge in Weekenders Adventures of The Land Before Time II: The Great Valley Adventure.
- Diesel 10 will be working with Lord Rothbart in Thomas the Tank Engine meets the Swan Princess get his revenge on Thomas and his friends by kidnapping Thomas along with Princess Odette.
- Diesel 10 will return along with Discord and Queen Chrysalis to join forces with Hexxus in Thomas the Tank Engine Goes to FernGully: The Last Rainforest.
- Diesel 10 will become Little Bear and his friend's enemy in Little Bear's Adventures of Thomas and the Magic Railroad, and later he becomes their big enemy by getting his revenge in Little Bear's Adventures of Pokémon Heroes, Little Bear and The Chronicles of Narnia: Prince Caspian, Little Bear's Adventures of Pokémon Ranger and the Temple of the Sea, Little Bear's Adventures of Pokémon: Giratina and the Sky Warrior, Little Bear's Adventures of Pokémon: Zoroark - Master of Illusions, Little Bear's Adventures of Sailor Moon Super S: The Movie, and Little Bear's Adventures of The SpongeBob Movie: Sponge Out of Water.
Diesel 10 is also a member of the Secret Warriors in Equestria Civil War, to bring in Ramicorn, who is the main villain.
76859Thomas was planning to keep Diesel 10 as the main villain in Thomas' Adventures Series, but decided not to so Devious Diesel will take his place as Thomas' enemy instead.