The instruction "1 Fear per Town/City this Power destroys" means that you generate some extra Fear if the power happens to destroy things. It's up to you to arrange how this happens, using the rest of the card. Tags: Mists of Oblivion
Generally, the "+" in threshold effects is just to remind players that the damage is in addition to the damage up in the normal effects.
(Mists of Oblivion changed between the second and third printings, and the current printings no longer have the "+".) Tags: Damage, Mists of Oblivion, Blazing Renewal