After finding a talisman in England’s most haunted ruin, three young boys awaken the ancient guardian of Berkshire Castle, which is hellbent on adding skulls to its collection.

What Richiev and Foxtrot25 said. ?What becomes the objective goal as a result of the situation created by the inciting incident? ?What must the young boys do -- or else?

Yet still it fails to say what the great challenge will be to undo this evil and when it must be done by.

Everything after the second comma is the problem because it focuses on the guardian's goals and not the 3 boys who I assume are the protags, kinda like The Goonies movie.

Agreed, great improvement over your first draft.