The Grendel Brood was a zerg brood.
The Grendel Brood was first observed on the Fringe World of Chau Sara. Alongside the Garm Brood, Grendel Brood warriors were situated throughout the Flannum Installation. However, Cerberus Recon Squad was able to battle its way through the warriors and extract key Confederate personnel.
During the fight to break through the Overmind's defenses, protoss leaders Fenix and Zeratul attacked the Grendel Brood's main hive cluster, killing its cerebrate and throwing the Brood into chaos. The stunning defeat also incurred the loss of the Baelrog brood, and allowed the protoss a straight path to the Overmind.
It was named after the monster Grendel from the ancient epic poem Beowulf.