Althought there is very little known about the different Broods that comprise the Zerg Swarms, some Terran scientists have attempted to document and classify a few of the larger Broods that have ransacked their colonies. It seems clear that each distinct Brood stems from a unique Cerebrate that carries out the will of the Overmind. Each Cerebrate is empowered to build its own Brood to accomplish its specified goals. Although the Broods are difficult to distinguish from one another, Terran scouts have witnessed that they vary in functionality and purpose. It has been noted that certain Broods work with each other in unison, as if they were operating as cohesive detachments of larger, tactical force. Terran explorers have named each discernable Brood with names of ancient beasts from old Earth mythologies.
Tiamat is the largest and most powerful Brood within the extended Swarm. It is speculated that the Overmind itself is protected deep within the safety of this living fleet. The most advanced Overlords and Queens define the rigid infrastructure of Tiamat and help to drive the lesser Broods to total domination over their enemies. Tiamat excels at tactical space combat and only dispatches its ravenous surface attackers under the most dire of circumstances.
The Fenris Brood is known for its superior tracking ability and is often called upon to hunt down escaped breeders and wayward enemies of the Swarm across wild terrain or through the endless void of space. Although the numbers of this Brood are few, it carries out its pursuit with merciless precision and cunning. Their primary role, however is to find new races and genetic strains that will benefit the swarm through absorption. Once an acceptable race is found, the Fenris Brood will hound it until it has been either assimilated by the Overmind or eradicated completely.
The Baelrog Brood consists of the most fearsome of all the Zerg warriors. Ravenous and bloodthirsty to the extreme, the Baelrog Brood is often called upon to sow terror and confusion amongst enemy ranks. Resorting to atrocious acts of cannibalism and indiscriminate slaughter, Baelrog typically causes enemy warriors to flee for their lives or turn upon their own kind in order to find some desperate means of escape from the horrendous Zerg onslaught.
Named after the fierce hellhound of Norse myth, Garm strikes with alarming speed and ferocity. The minions of this Brood excel at hit and run raids that weaken their enemy's defensive formations. Zasz, the cunning Cerebrate of this Brood, delights in preemptive attacks, relying chiefly upon surprise to throw enemy forces into total chaos.
The Jormungand Brood is one of the most heavy-handed of the Zerg attack forces. Typically called upon to follow Garm's preemptive strikes, Jormungand Brood pacifies all other resistance to the Swarm. Jormungand relies on strength of numbers and brute force to overcome any foe and excels at ground-based combat and direct unit-to-unit warfare.
Should the Jormungang Brood fail to achieve total victory over an enemy force, the Surtur Brood is released into the combat zone. Named after the fiery Titan of destruction from Norse mythology, the Surtur Brood is let loose upon any remaining enemy warriors. This Brood is so completely destructive when unleashed it is kept restrained within the recesses of the Zerg fleet and is only called upon under the most extreme circumstances. The Surtur Brood has been known to eradicate friendly Zerg troops as well as enemies in its furious rampages.
