The Great Beings wanted more elements than the main 16 elements, including the secondary elements. So, they attempted to make 6 other types of Toa with elements from the periodic table, because these elements have unique properties. One type of toa they made was a Toa of Fluorine. Due to the fact that Flourine reacts with almost every substance, including protodermis, these toa lived a very short life. Only one was made by the time Mata Nui escaped the doomed Spherus Magna. This toa passed on it's power to one matoran after it, and a lineage started. This lineage most recently came across this Matoran, which by this point, The Nygrah Ghosts found a way to lengthen their lives, and increase their elemental efficiency. Although their methods scarred the toa beyond recognition, and he found himself abandoned by all his friends. He still roams Spherus Magna today, helping beings along the way.
I'll let the pictures do the talking for now.
This is the MOC I am currently working on, whoever can guess what it is, is great.
(It's an upgrade of an old MOC)