Increases the critical strike damage bonus of your ranged abilities by X%.
Mortal Shots is a Hunter talent in the Marksmanship tree that increases the ranged weapon critical strike damage bonus of your special shots. It does not affect your chance to get a critical strike, but instead increases the damage that your critical strikes do. Note that it is an increase to the critical strike damage bonus and not a straight increase to the damage dealt by critical strikes. The talent is a prerequisite for Aimed Shot
Since the talent has no effect if you do not land any critical strikes, it is less useful at lower levels when your critical strike chance will be much lower. Because of this, the talent's main value at lower level is to allow you to pick up Aimed Shot.