The Bohrok are controlled by krana, mask-shaped creatures that lurk beneath their transparent faceplates, determining the host Bohrok's rank, power and motivation. Each Bohrok or Bohrok Va has its own distinct krana color, with eight krana shapes representing ranks that range from the elite Swarm Commander to the common - but powerful - Clearance Worker.
Each Bohrok and Bohrok Va includes a random krana in its individual color. Krana packs are also available separately, each including three random krana and two Kanohi masks, one gold and one silver. Besides conferring great power on the Toa, the silver and gold masks can be worn by the Toa Kaita, a pair of mighty heroes formed from the parts of three Toa each.
And what if a krana should find its way onto a Toa? Perhaps the Toa would learn to control the power of the creature and master its secrets. Then again, perhaps the Swarm would have a new recruit…