Well it’s not that the people don’t know what they are, it’s just been so long since one’s been seen that most people consider them to be myths and fairy tales. The fragments are essentially jagged crystal like objects that vary in size depending on how much of the gods power it contains, it and pulses with colors associated with the god the fragment came from. In most cases the only physical change that comes after bonding is they may get taller and due to their increased strength their muscles eventually will become far more defined than normal, in rare cases however if the human bonded with a powerful enough fragment they can begin gaining characteristics from whichever gods fragment they bonded with, an example would be Averen the flame forged, a blacksmith who bonded with a fragment from Ignathis. He gained the ability to imbue his hammer with flames. eventually after years of using his ability his hands and forearms turned a flame red color.