That was due to the loss of the parallel souls associated with them.
The same with the weapons that had cores. Or, as they were generally known, soul weapons. Due to the fact that they were connected to the owners' souls, their loss would have an adverse effect on the main soul of the owner.
Since the largesword was on a self-destructive path and was powered by the seal, it managed to shatter the massive claws. It struck the death-eater at the center of its heart or where its should be.
