Hive

The hive is the key that unlocks the final stages of zerg evolution. Protected by a dense exoskeleton and granted full access to the Overmind's pool of knowledge, it continues to provide the same functionality that it has since it was a hatchery (birthing larvae, maintaining creep, and digesting minerals/gas). Once the hive is present, the cerebrate commanding it has the potential to unleash the full fury of the zerg.

The genetic model for a hive is extremely complex, and would be indescipherable by any terran scientist.

StarCraft II
The hive reappears in StarCraft II. The hive can set two rally points, one for most units and one for Drones.

Each individual egg can be separately rallied; this overrides rally points set for the hive.

Upgrades
The lair researches an upgrade for the overlord, giving it increased speed and transportation abilities.

The lair researches a speed upgrade for overseers as well.