A character or object whose location is unknown to 1 or more opponents is hidden from those opponents. An opponent may not physically target a character who is hidden from him with any action requiring line of sight or any skill check with the Vision tag. Further, when a character makes an attack against an opponent within Melee Range from whom he is hidden, the target is considered to be flankedA character is flanked if 2 opponents stand on directly opposite sides of him and within Reach or CQB Range. Opponents may only flank an adjacent character when unarmed or carrying a ready melee weapon, or a non-adjacent character when carrying a ranged weapon. For examples, see the Flanking Diagram. When a flanking opponent makes an attack against the character he’s flanking, he gains a +2 bonus with his attack check (if making an unarmed or melee attack), or a +1 bonus (if making a ranged attack)., even if no teammate or ally is located on the other side of him. If the target is unaware that any enemies are present, he is considered vulnerableA vulnerable character loses his Dexterity bonus to Defense (if positive), as well as all dodge bonuses to Defense. He may also be targeted with a variety of special effects, such as sneak attack damage. during this attack as well. Immediately following the attack, the character ceases to be hidden from the target.