What does Sonia’s book do?

What does Sonia’s book do? Sonia’s Book is a key item introduced in Generation VI. It is described to record Sonia’s discoveries about Galar’s Darkest Day legends, but the item cannot be used or read.

Sonia’s Book is a key item introduced in Generation VI. It is described to record Sonia’s discoveries about Galar’s Darkest Day legends, but the item cannot be used or read.