Board Thread:Questions and Answers/@comment-31067473-20170629215035/@comment-13682699-20170630000233

It means that their SOUL is no longer existing. They are gone forever. The only way to bring them back is to possess the power to SAVE/LOAD/RESET to bring the monster back entirely by essentially going back in time to a point when they were alive.

No one knows what happens to a SOUL that shatters or the monster who dies.