Eonus was created accidentally by the Great Beings, as a spontaneous result of the creation of the Toa Mata. Due to this, he is six times the size of a Toa, and six times more powerful.
After his formation, Eonus destroyed the lab where the Great Beings were creating the Toa, and escaped. In doing so, he put an end to the production of further Toa(the Great Beings had plans for many more), forcing the Great Beings to give Matoran the ability to transform into toa.
Eonus: You dare challenge me?
Firehazard: What is this arrogant fool doing?
Firehazard: AHHH!! Put me down!!
Eonus: I don't even need to use my powers on you, besides, this is far more fun!