Note: This is part of the setting of the world that our Steampunk personas come from, which is also content for the game we are working on.
Very little is known about diesel; but what is well known, is the sound of the diesel combustion engine that signals the approach of sky pirates. The smell of fuel and smog that fills the sky is an ominous sign of danger. No decent person of good standing would ever consider the use of diesel… a form of energy used solely by the vile underclass of thieves and murderers. This minority is a dangerous one, with spider like airships that attach to the underside of floating rocks, waiting silently for an unsuspecting Zeppelin or Airship. When they attach to the underside of a passing vessel, the sound of the diesel engine gives only a short window of opportunity to act before the pirates board the ship.
Just as fowl as their ships, are their weapons – chainsaws and buzzsaws that tear through metal. They leave a wake of misery and a mess of mangled parts behind them. One visit from a pirate crew can decimate an airship – even as far as to fall from the sky, plummeting to what is left of the hollow earth below.
The least dangerous encounter of a pirate is on land. They ride diesel motor vehicles that can outrun most steam powered locomotives. In fact, they can run at par with most steam engine trains… of which they will typically loot cargo from. Pirates can still be a devastating encounter on land, especially if trains are derailed or people loose lives for getting in their way.
So, always beware of the sound of the combustion engine, because it will save your life some day.