Hiveminds are thaumic ships that are piloted by extremely powerful magi that can control a large number of smaller thaumic ships. The magi project their will into the pilots of smaller thaumic ships, controlling their actions as they see fit. Due to the rarity of magi being able to wield such power, hiveminds are also quite rare.
Like regular thaumic ships, hiveminds are composed of an aeternically-sensitive metal frame that the Magi can then manipulate as they see fit. However, the main difference is that the frames seen in hiveminds are often much larger than regular thaumic ships, sometimes reaching the size of corvettes. This is largely due to the fact that many powerful Magi often feel uncomfortable being confined to the smaller frame of a regular thaumic ship.
In battle, hiveminds are capable of firing beams of Aeternal Energy from their surfaces like regular thaumic ships. However, their real power comes from the ability of the magi piloting the hivemind to manipulate a large number of smaller thaumic ships. They do this by projecting their will across the Lux Aeterna and into the minds of magi who pilot these smaller vessels. This allows them to greatly improve the coordination of their peers.
However, this power comes at a price. The magi being manipulated will often go into shock after the magi piloting the hivemind gives them control of their actions back. This is often enough to drive many weaker magi insane, which inadvertently makes them suitable candidates for piloting lux bombs.