Constructs
The earliest forms of Constructs went by the name "Golem". A golem is a humanoid being created to act as a slave, guardian or messenger. Examples of these are Homunculi, Shield Guardians, Helmed Horrors and, of course, the various golems (flesh, wood, clay, iron, etc.).
These golems were, generally speaking, without intellect. They could be programmed to performed a small number of tasks but nothing complex. However, a drow mage was able to to successfully transfer a small portion of his life-force to a homunculus and this creature developed a distinct personality. Later experiments by the archmage, Savinfrow and the Shadow Lord, Landryn, showed how the spirits of the recently deceased could be used to animate large numbers of these constructs and to provide them with the ability to learn far more than a few basic tasks.
When the Merebian Empire started to lose the war with the forces of the General, the Emperor Justinian decided on a bold course of action. He was to rescind the law prohibiting the use of arcane magic and would employ the group known as the 'Cerulean Order' to mass produce an army of constructs. To bring them to life he would use the souls of recently departed Imperial soldiers, and the Guild of Tinkers (a loose collection of Gnome artificers) would be given the materials to create as many bodies as necessary.
Over the space of five years over 40,000 "forged-men" (as they were colloquially termed) were constructed and deployed. Eventually, the General called a truce ad a treaty was drawn up limiting the expansion of the Empire eastwards. This treaty (the "Treaty of the Eight Thrones") stands in place to this day. Soon after this though, the remaining active Constructs began to exhibit odd behaviour. Although none of them recalled their former lives in detail they slowly started to take on the names and personalities of the souls that inhabited them. Eventually, large numbers of Constructs demanded to be set free from military service and many took up the careers they had in their former lives.
In order to limit an adverse effect on the Empire by admitting that the souls of many Imperial soldiers would never reach any promised afterlife, the Constructs were given their own lands (now known as "The Forgelands"). The Guild of Tinkers were entrusted with maintaining these people and to discourage any "wandering" into human lands. Nonetheless, some Constructs have been able to leave the island and take up employment within the Empire.