In many technologically advanced societies, droids are designed to handle a multitude of mundane tasks. The organics who created Iokath embraced this idea, and built a wide variety of mechanical servants to nurture their artificial world. Custodian and compactor droids were created to preserve the parklands; scour swarm droids to clean the Chromium Garden; purifier droids to provide protection and security; and support droids to maintain and repair the entire system.
With the extinction of their organic masters, the purpose of these self-perpetuating service droids slowly changed. As newer generations evolved, their original mandates shifted from preservation of Iokath to aggression toward any foreign entity.
The escalating xenophobia led to virtually every droid on Iokath becoming weaponized in some way, eventually culminating in the creation of the Colossus Droid, a war machine with enough firepower to wipe out an entire army.