You... don't craft them... you need to go to the Sewers, under spawn, (mistress/master rank NEEDED) and you trade them to the Shady Merchant. Now, if you found a bug, give the staff members evidences that you had those fragments so they can reimburse it.
Heya, I was in the server when clark was talking about this. He said he went to the black market and purchased it but it ate his fragments. (Due to him not having the cores on his person) Clark, head on over to https://stickymc.com/bug-reports/ and submit a bug report.