Somnus

Somnus is a failsafe developed by Dr. Sandra Loew implanted into hydralisks of Project Tamed. When activated, Somnus would trigger a reaction in the cerebral lobe created by the pathogenic prionic organism that would cause a cascade of irreconcilable neural signals, leading to the death of the hydralisk in seconds.

When Dr. Loew turned the Project Tamed hydralisks against Garr for using her hydralisks against terrans, she activated Somnus to end the project. However, it was revealed that Sonmus did not work, and the hydralisks were feigning allegiance to the Dominion ub a plan by Sarah Kerrigan to eliminate high ranking Terran Dominion officers.