Stalk Unseen (Passive) If a model with this special rule is partially concealed from view by a piece of terrain, they cannot be seen at all at distances of more than 6" - they appear to melt into the background. This means that enemies cannot Charge, Shoot, or target them with Magical Powers of special rules at ranges of greater than 6", unless they have a completely clear view of the target.
If the model is ridng a mount, Stalk Unseen has no effect.