Utterly Mad

You bow to the King who smiles in response. He motions for you to stand straight again and you do so. The King finally speaks, saying "There have been reports of odd things out near the edges of our territory bordering the Great Forest. Things that are of an unnatural design."
You look at him and ask "What, pray tell, is the nature of these things?"
The King proceeded to inform him of entire towns disappearing without a trace of anything, no fighting, and no trace of the town ever having been there. Then there were the tales of long dead people returning to life and walking back to their old homes. And the tales of the 'burning beasts' that devoured men and killed the innocent.
The King sighed and finished by saying "And all the patrols sent out to investigate have not returned. I fear that the magic of the Great Forest is being warped, and what that could mean I do not know."
You do not respond for a few minutes, the thoughts flashing through your head keeping your tongue still. If the magic of the Great Forest was being manipulated for evil, then the one responsible had no idea what he was doing. Even the necromancers had signed a pact to never manipulate the energy of the Great Forest, for fear that they could destroy the world as they knew it. That they could cause the beast that the Great Forest had been keeping imprisoned to be released, and then nothing could save the world.

Do you tell the King about the possible outcome if someone truly is manipulating the Great Forest's power, or do you try to ease his mind?