He is a mostly benevolent authority figure who helps the engines out of their scrapes, but engines that defy him or disturb the peace are punished. In an early episode he left an engine bricked up in a tunnel. Quite a few engines have also been sent away as well.
It is slightly funny to see childhood again through adult eyes but I'm not sure what I'll do when my son is old enough to understand these things. Im sure the idea of being left alone in a tunnel would have terrified me as a child. :)