That his own grandson will be the cause of his death
Information that can be transformed into evidence is when it can be used
to support or refute something. Evidence usually means that it supports
or refutes a case or claim by someone. So in order for the information
to be used as evidence it must be useful one way or another.
The Sorrows want the Lucera, the spiritual leader of the shadowshapers, to become one with them and "set them free." And shadowshapers are humans who can put spirits into the things that they create (art, stories, etc.) and make their creations come to life. But that's just about all we learn
