If a character attacks an enemy from behind (starting his activation in a square behind his target) he will get a bonus to hit (see the modifiers in the Ranged Attacks and Melee Combat chapters). Additionally, the defending character will not be able to use his shield.
NOTE: Remember that if a character wants to attack an opponent behind him, he must first turn or change facing during his activation (which is not regarded as Movement nor as an Action), in order to have Line of Sight to him.
(A) Borgron's engaged with the orc. If he wants to disengage, he must pass an Agility test. Another option would be to move Shara adjacent to the orc. In this way, Borgron could move freely, since Shara would be engaged with the orc. The dwarf could also move (no need of passing a test in this case) to an adjacent square, as long as he doesn't leave the orc's melee range and providing he uses his Action to attack the orc. (B) If the orc advances to one of the squares adjacent to Shara, he must stop his advance there since he will have entered her melee range (as long as Shara is not engaged with another opponent). (C) Taeral intends to reach orc (1). He has no problem to do it since Borgron is engaged with orc (2). That means Taeral can move through the orc's Melee Range (3) and avoid the troll’s melee range in order to reach his target. Shara cannot disengage from the troll. In fact, if Taeral were to enter the melee range of the Large creature, both heroes would be engaged, because they are smaller than the Large creature. If the troll doesn’t turn towards Shara, Shara will be considered to be attacking the troll from behind, as her initial position will start at the creature's back.
If an attacker can perform several attacks, these will be resolved separately. A maximum of 3 attacks can be made by one character, regardless of the combination of weapons or abilities he is using. Huge creatures are excluded from this rule.