Weapons of Ma'chello's design, capable of penetrating the skin and infiltrating the body. They are designed to exit from falsely marked Goa'uld tablets, seek out and destroy the Goa'uld within, freeing the host from enslavement to the symbiote. If there is no symbiote the side effects are akin to schizophrenia.
Once the Goa'uld is destroyed, the killers vacate the body through the ear. Ma'chello's voice can then be heard, reciting the words "You have delivered me to the vile Goa'uld so that I may destroy it."
Legacy - Jackson, O'Neill, Carter, Fraiser and Teal'c succumb to a number of Ma'chello's Goa'uld killers.