These were one of many types of weapons created by Ma'chello to combat the Goa'uld Empire. The Goa'uld Killers were placed within Goa'uld page turning devices when interacted with a specially made tablet. Once the page turner was used on the tablet, 10 small white grub-like worms would fall from the device. They would immediately begin to find a host body and infect it. Hosts that possessed the protein marker that signifies a body where the symbiote has died signals the small machines that the Goa'uld is dead after which the Goa'uld Killers deactivate. (SG1: "Legacy")