From the introduction:
Age of Steel is a dieselpunk roleplaying game set in the world of Neres; a world not unlike our own in the first few decades of the 20th century.
Neres has just emerged from its first global conflict; a war known as the Great War in which hundreds of thousands of men and women died in the mud and horror of the trenches.
Technology in Neres has taken a slightly different route to our own world; personal mecha powered by diesel engines are used for numerous applications from war to common labor; huge airships ply the airways; bipedal automata act as servants for the rich and gadgeteer inventors construct homemade rayguns in their basement laboratories.
In the wake of the Great War Neres is a hotbed of political scheming and economic growth. Industry and commerce have come to rule the world which, thanks to the airship, aeroplane and radio is rapidly becoming smaller. It is a time of innovation and advancement, as well as a time of chaos and conspiracy. Little do the majority of people know but an ancient evil is at the heart of the conflict in their world. Eldritch monstrosities from before the dawn of time seek to unmake reality, aided by cults of insane worshipers.
Into this world come the player characters; free agents and soldiers of fortune looking to find their way in a new and dangerous era of adventure, technology, intrigue and hidden evil.