The Hive is the realm of the Intrusion, the Fear of Insects and Vermin. As a result, it appears as an ant colony, with tunnels up to 80 meters tall and thousands of kilometres long. Within these tunnels it is shown to have many complex "sub tunnels" that are human sized, with crouching sometimes required to traverse them.
The Hive is home to thousands of Drones each one having various stages of infection: from those who were just contacted by the Intrusion, to those fully infected, insectiod abominations. Insects of massive size constantly sury and creep along within this realm, skittering about and taking food (human beings) to their lord and master, or consuming the victims themselves.
There are massive "breeding" chambers for these insects, which are truly horrible to behold, thousands of squirming, grotesque grubs groping and crawling towards food (read: humans) that is thrown near them.
Within the center of this massive , complex structure, the true for of The Instrusion has been reported as living within a chamber that is larger then the entirety of the island of Manhatten.