Prometheus was a Greek Titan. Possibly one of the most important Titans, as he stole fire from Zeus and gave it to the humans. This system was developed to resist those forces through technological means.
In a small, genetically isolated region it is not uncommon for the locals to have three arms. The third arm is generally a second right arm that is a good bit weaker than a normal arm and is generally held against the chest. This hird arm is most often used to carry small things, though some of the more skilled craftsmen have learned little tricks with their third arm.