As opponents who are actively aware of a threat are not subject to a surprise roll, characters with this ability cannot backstab defenders in the midst of an ongoing melee or when engaging an opponent who was previously aware of their presence. Surprise ~ and therefore backstabbing ~ can only occur when the intended victim is wholly unaware of the attacker's intent, then fails surprise when given an opportunity to defend themselves.
Unskilled BackstabbingThieves who do not possess 10 points of knowledge in backstabbing will be treated as 'unskilled' at the art. A successful hit will yet cause double-damage, but unskilled thieves will receive only a +2 bonus to hit when surprise is achieved. Additionally, such thieves will be limited to the use of daggers, short swords and hand-axes. They will not be able to backstab using other weapons.
Note for Assassins: Only thieves are entitled to unskilled backstabbing as a class skill. Assassins are not considered to be able to backstab unless they have the knowledge to be amateurs.
AmateurThere is only one amateur skill associated with the study of backstabbing and it can be described quickly. Characters with this ability (largely thieves and assassins, though others might possess the talent) will gain a benefit of +4 on their to hit die when attempting to backstab. To do so, they are able to employ any bladed weapon, including axes, swords, daggers, pole arms, spears and the like. They are still limited to attacking from within melee range.
Note that if the defender is stunned but yet alive, neither backstabbing nor assassination cannot be attempted again.
Assassin's Sage Abilities
Thief Sage Abilities