Blister I the Small Twin Diesel

Blister I is one half of a pair of brothers who work on the Arlesdale Railway. They both arrived to help construct the railway, and also carry out shunting duties. However, they were torn apart after a serious accident, in which Blister II was away for around 20 years. Now he is back in working order, and both of them have proven to be really useful diesels.

You can read about him in the Sodor Island Forum's ERS Library, in the following books:
ERS 75- Sudrian Twin Engines
ERS 83- Small Railway Discoveries
ERS 116- The Small Controller's Engines