From New Babbage Department of Records and Archives
When the Cloud Angels dissapeared from the strange machines which ran the empire there was a rush to find a new source of energy. It is a universally held truth that within fifty years coal replaced the once endless energies of the Cloud Angels as no other source was ever readily found.
However, there are hints and rumors and even some evidence of other machines which were built in the wake of the fall. These machines are modified versions of the cloud-angel designs and are very similar in their design with the exception that the reaction chamber is not the blank hole familiar in those machines that supposedly ran on Cloud Angels, but rather a curious arrangement of restraints which might be used to hold a person no larger than a small child.
It is darkly rumored that the machines were, in fact, run, somehow, on children and this accounts for their relative scarcity: they were destroyed by those seeking to protect their youth from such reckless use and it is believed that the term "children eaters" as applied to some engineers may come from this dark chapter in our history.
It should be noted, though, that there is a smaller faction who believes these machines were run by quite a different source, and to them they are referred to as "Singularity Machines." Though what the fuel source may have been few have ventured a guess at.
It is believed that only one complete Singularity Machine exists, though where it is kept, no one seems quite sure of.