The letter said:
Dear Jon,
I have written this letter, in addition to the one I've placed with the stone, to warn you about a dark entity that has frequently tried to possess the stone. He has chased me across the world and back again. I am too old to outrun him anymore. I hate to make it sound like having the stone is a burden. It's not. Using it the right way will benefit many, as I have done. And I am certain that you will too.
Be alert, Jon. This entity can take any form.
Your friend, always,
Grandpa
Jon wasn't sure what to think. An evil entity that wants the stone?
