Rheneas is a narrow gauge tank engine. He speaks with a Welsh accent.
Rheneas was built by Fletcher, Jennings and Co. at Whitehaven and arrived on the Skarloey Railway sometime around 1866.
Unlike Skarloey, Rheneas was stern and thoughtful, and fell out with Skarloey after the latter called him a "stick-in-the-mud" following an argument over cabs. The 2 reconciled after Rheneas saved Skarloey from a landslide.
Rheneas literally saved the railway by keeping service through through a very lean period in the late 1940s. By 1950, Skarloey was in need of repairs, leaving Rheneas to run the line. He managed to pull a full train home one rainy day despite jammed valve gear, and thus was rewarded with an overhaul. His overhaul took place in 1961 and was returned to the Skarloey Railway soon after.
Rheneas returned to service in 2002 after an overhaul that was started in 1999.
Rheneas is happy and cheerful, but because of his age, he often breaks down.
Rheneas has become somewhat immature and reckless, such as when he decided to take the dinosaur skeleton on his own and took part in the race with Freddie. However, Rheneas has been kind and helpful as when he decided to take Skarloey's coal trucks to the Wharf as a surprise for him. Despite the fact that the coal trucks went missing thanks to Peter Sam, the gallant little engine was able to give Skarloey a much needed rest. Likewise, Rheneas helped Skarloey when he got stuck in Percival Pond with the puppet show special.
In RWS, Rheneas is painted in the Skarloey Railway's red livery with blue lining and his name painted in gold on his boiler.
Rheneas is painted vermillion with gold and black lining. He has a gold nameplate and number plate on both sides. In Blue Mountain Mystery, he was repainted yellow with blue lining to play a joke on Thomas. He was painted back into his original colors soon afterwards. For unknown reasons he is colored a reddish pink in all merchandise ranges, except the Bandai TECS range.
- In New Little Engine Rheneas is depicted as an 0-4-2.
- His name is Sudric for "Divided waterfall".
- In the French adaptation of the television series, Rheneas is called "Philéas".
- Rheneas' whistle sounds like 2 medium blasts.