So, first off, picket's sword was made of an unknown metal found at the slave camp, I didn't really like how Sam skimmed over this. I think like how Heather's dreams/visions came back later on to remind us.

what if picket's sword, is special?

We know that Flint forged the first sword. I thought perhaps he forged his sword and maybe his fragments/leftover metals did something and perhaps... no.... but what if Picket's sword is part of Flint's?

It was just a thought that came in my head, I don't really have much proof sorry.

-@Dikko_The_Squolf