Infusion Incident

The Infusion Incident was the cause of the Grunt Rebellion. Kig-yar agents secretly infused the Unggoy's Infusions, rendering a significant amount of the male Unggoy population sterile, in order to keep the ever-growing Unggoy population in check. Eventually, the Kig-yar's conspiracy was uncovered, resulting in all Unggoy beginning an organised and bloody insurrection against the Covenant, with their first target being the Kig-yar's eggs.