Krana Za were Krana that could communicate telepathically with other members of the swarm. This made it easy to send and spread news and information among the swarm. Each Toa Mata had to collect one Krana Za and the other seven Krana to unlock the Exo-Toa chambers.
Lewa and Matau were both under the control of a Krana Za when they were captured. Matau's was taken off by a few free Matoran and Lewa's by Onua.