Mighty Mac is a powerful but inexperienced double-ended Fairlie duplex locomotive working on the Alun Railway. Mighty, the more gruff of the pair, sports a flick of hair over his forehead, while Mac, the younger, sports freckles.
Mighty Mac was built at Boston Lodge, in 1886, as one of a number of double-ended locos built for the Ffestiniog Railway over the years. However, the plans changed when Caderyn Gerralt won ownership of Mighty Mac in a drunken card game with the Ffestiniog Railway's dark horse, Charles Easton Spooner and Mighty Mac joined the Alun Railway Fleet.
Mighty Mac currently works in the shunting yards, preparing trains and moving trucks and also serve as a lackey to Arwel.
Mighty Mac is a powerful but inexperienced engine, easily influenced by those of a more dominant manner, as seen in their loyalty to Arwel. While the pair argue a lot, they are strong when they work together.