There is a reason why Krana-Nui is called Krana-Nui. It is because long before the matoran lived in 12 villages there, the Krana lived there.(For those of you who don't know - Krana are small, but intelligent mask-like creatures. They made their only appearance when the Bohrok attacked Mata-Nui)They were by far the most technologically progressed creatures in this world. They had mechanoids which they controlled using their minds. There weren't many kinds of mechs, but each one had it's own specific purpose.