Rheneas was built by Fletcher, Jennings & Co. in 1866, the same time as his twin Dolgoch. Dolgoch was sent to the Talyllyn Railway in Wales, while Rheneas was sent, by ship, to the Skarloey Railway on Sodor, where he met his brother, Skarloey.
Rheneas has been called a "gallant old engine" before and deserves such a title. Rheneas is highly determined, brave, courageous, and a long-time friend and brother of Skarloey. He is a tough, committed worker despite his age and takes great responsibility in his work. He is keen to keep his friends smiling and, although he is a level-headed engine, he can be a bit of an adventurer too. Though he may often try to struggle on alone, Rheneas knows when it is time to call on the help of his friends. Nevertheless, Rheneas is always highly dedicated to the task at hand.
Rheneas is painted vermilion with black lining and brass fittings. He has gold and black name and number plates on the sides of his boiler and coal bunkers respectively.
- His name means "Divided Waterfall" in Sudric.