Each puzzle has a particular relation with the past of our world. This changed the aspect of each puzzle.

However, the rarity that haunts each piece is determined by the corrupted energy used by SOF to create more of them. 

The most rare pieces are untouched and remain unique. They were not in contact with the energy of SOF. 

Some pieces were multiplied 7 times, while others were flooded with cursed energy and have up to 42 copies of themselves. 

Watch carefully which one you have and which one you are missing; for some are rare indeed.