Nia is a tank engine from the African country of Kenya and a new member of the Steam Team on Sodor. She is a real optimist with a great sense of fun. She is also driven by a strong moral compass and takes being fair and kind to others seriously. She is not afraid to speak her mind when she needs to. Nia is both thoughtful and practical and often comes up with very creative ideas. Her kind heart and infectious enthusiasm never fail to win over others in the end.
She first met Thomas in her homeland of Kenya when he stopped in her yard to collect more trucks to take to Dar es Salaam while in pursuit of Ace. Noticing how heavy his train is getting, she offered to help, but Thomas sternly refused, stating he could handle it himself. However, she later arrived to help him over a steep hill when the trucks nearly caused him to slide back down it. She later encouraged the trucks to sing to raise Thomas' mood during the journey, and to help soothe an elephant that tried to charge Thomas when it was blocking the tracks. When they reached Dar es Salaam, Nia had a chat with her friend Kwaku, but Thomas interrupted before Nia could reveal that her shed was destroyed and she was looking for a new one. After Thomas thanked her for her help, he prepared to board a ship bound for South America and the city of Rio de Janeiro in Brazil. However, Nia decided to join him, much to his chagrin, having wanted to see the world herself.
Thomas remained unfriendly with Nia throughout their journey, but began to warm up to her after they rescued a crashed Ace and made it through the Amazon rainforest after some difficulty, continuing their journey through Central America and Mexico before reaching North America and the United States. As they made their way through the Grand Canyon, Ace tricked Thomas and Nia into splitting their delivery to San Francisco between them and racing to see who is the faster of the two steam engines. Thanks to Ace, who wanted to get to the Bonneville Salt Flats, Nia was separated from Thomas, and as a result, thinking that Thomas was in on Ace's trick, she became hurt and cross, and continued on alone to China.
When Thomas caught up to her in the Himalayas, she refused to listen to his explanations for what happened, still hurt and upset about it, but hearing his heartfelt apology, she realised he never meant to upset her and was truly sorry for it. Before she and Thomas could fully make amends, an avalanche caused by Thomas trying to get Nia's attention swept her off the tracks and left her dangling precariously over a cliff. Thomas attempted to pull her back to safety, but a rock underneath her was dislodged, causing her to go over the edge and nearly pull Thomas with her, until Yong Bao arrived just in time to save both of them. After Nia was lifted back onto the rails by the breakdown cranes brought by Yong Bao and The Chinese Diesel, she and Thomas prepared to return to the Island of Sodor, with Yong Bao advising they travel through Asia and Europe to get back to Sodor via The Mainland.
Together, Nia and Thomas made their way back to Sodor, unaware of a signalman in India seeing Thomas and phoning ahead to let the North Western Railway know he was coming home. When they reach the Vicarstown Bridge, Thomas realised that once he crossed it, he would be home, but Nia would have to go home to Kenya. However, Nia revealed what she had tried to tell Kwaku back in Dar es Salaam before Thomas interrupted her, that she no longer had a home to go back to. Sympathetic to her plight, Thomas offered Nia the chance to stay and work on the North Western Railway, knowing that Sir Topham Hatt would love to have Nia working on his railway. The two engines crossed the bridge, returning to Knapford to find a large group of Thomas' friends, human and engine alike, welcoming him home. After Thomas formally introduced Nia to Mr. Percival and the others, Nia prepared to enjoy her new home on the Island of Sodor.
While enjoying her new life on Sodor, Nia bonded with Gordon when he was upset over Edward and Henry moving out of Tidmouth Sheds by reminding him they were still his friends, revealing to him that she felt the same way due to all of her friends being back in Africa. She later learned about reading numbers with some help from Annie and Clarabel. However, she also fell victim to Bill and Ben's tricks when they made up a game called "Hunt the Truck", and Edward had to step in to make them give back the truck they hid from her.
Like in the television series, Nia bonded with Gordon when he was upset over Edward and Henry moving out of Tidmouth Sheds by reminding him they were still his friends, revealing to him that she felt the same way due to all of her friends being back in Africa. However, she also fell victim to Bill and Ben's tricks when they made up a game called "Hunt the Truck", and Edward had to step in to make them give back the truck they hid from her.
Nia is an adventurous and fun engine who teaches Thomas about friendship. Whether she is in her homeland of Africa or travelling around the world, Nia is positive and thoughtful. Her eagerness to help can sometimes irritate her friends, but her truthfulness and kind heart always win them over. She is a good problem solver, although she once had trouble reading numbers until Annie and Clarabel helped her.
Nia is based on the KUR ED1 class, a class of 2-6-2 tank locomotive built by Vulcan Foundry for the Kenya-Uganda Railway between 1926 and 1930. Primarily used for shunting duties, they were also used to haul branch line trains. They were later operated by the East African Railways and were reclassified as part of the EAR 11 class. One member of this class, No. 327, has been preserved at the Nairobi Railway Museum in Nairobi, Kenya.
Nia has been modified in order to work on British railways. Whereas her original basis was metre gauge, Nia is standard gauge and she has been given buffers and screwlink couplings in order to work with the other engines.
Nia is painted orange with yellow lining. She has stripes with an African pattern consisting of red, yellow, green and purple painted along her tanks and dome, as well as green and yellow lining on her cylinders and green stripes on her brake pump and her footplate is painted red. Her name and the number "18" are painted on the sides of her tanks and cab respectively in yellow within black squares.