Kollos

The behemoth of the Hive Born is a living tank and siege engine. Its great strength is usually used to build and dismantle hive structures. Their armor seems almost impenetrable and when they begin to move and gain some momentum, they are near to unstoppable. Astonishingly, their enormous carapace is hollow to a great extent. Sometimes, material or even smaller hive creatures are transported in these hollow spots. On other occasions, they transport eggs or nourishing goo under their carapace. Is is rumoured that the hollow carapace enables them to float on the water and serves other Hive Born as makeshift raft, but such reports are rare and rather dubious. Until now, no one has encountered a Kollos away from the hive so such rumours are probably just exaggerations. On rare occasions, though, it has been at least observed that a group of Kollos builds bridges or ladder-like structures with their bodies which are used as passage by other Hive Born.
Another observation seems more disturbing, though: Sometimes it seems that the Hive Born fight more coordinated and almost strategically intelligent when they are close to certain Kollos. This led to speculations that another, still undiscovered, hive creature might ride the Kollos from the inside and commands its brethren. However, until now, no Kollos that has been defeated had harboured such a creature.
In the constant war against the Deeplings, the Kollos are only of little use. Unable to dive or navigate very narrow passages, they are primarily used to repel the advances of the Deeplings. Here they serve the other Hive Born as tanks and shields while inflicting massive damage upon opponents careless enough to get into their reach.