"Do what you will with my servants, Cerebrate. They will serve you unquestioningly. Go now, and bring swift wrath to all who oppose the Swarm." -Cerebrate Daggoth, upon granting control over some of his Hunter-Killers.
The Zerg Hunter-Killer is a breed of Hydralisk used primarily by the Tiamat Brood, ruled by the elite Cerebrate Daggoth. It has twice as much attack strength and hit points as the Hydralisk, and has the Muscular Augments and Grooved Spines upgrades even if you have not researched them.
Zerg Exodus: A detachment of Hunter-Killers was sent to help the Zerg safely evacuate the Chrysalis from Tarsonis, which had been blockaded by a small Protoss fleet.
Infiltration of the Amerigo: Two of these assisted Kerrigan when she infiltrated the Dominion Science Vessel Amerigo to remove the effects of her Ghost conditioning which hampered her now deadly psionic powers.
Defense of Tarsonis: Several Hunter-Killers were liberated by Kerrigan after Daggoth lost control over his brood upon the Overmind's death on Aiur. When the UED acquired the Psi Disruptor, Kerrigan used these HKs to protect several Zerg Hives from renegade Zerg.
Assault on the Psi Disruptor: Several renegade Hunter-Killers were found on Braxis along with Devouring Ones and a Torrasque during the attack on the UED-controlled Psi Disruptor.