Backstab

Thieves are weak in toe-to-toe hacking matches, but they are masters of the knife in the back. When attacking someone by surprise and from behind, a Thief can improve his chance to successfully hit (+4 modifier for rear attack and negate the target's shield and Dexterity bonuses) and greatly increase the amount of damage his blow causes.

To use this ability, the thief must be behind his victim and the victim must be unaware that the thief intends to attack him. If an enemy sees the thief, hears him approach from a blind side, or is warned by another, he is not caught unaware, and the backstab is handled like a normal attack (although bonuses for a rear attack still apply). Opponents in battle will often notice a thief trying to maneuver behind them - the first rule of fighting is to never turn your back on an enemy! However, someone who isn't expecting to be attacked (a friend or ally, perhaps) can be caught unaware even if he knows the thief is behind him.

The multiplier given in Table 30 applies to the amount of damage before modifiers for Strength or weapon bonuses are added. The weapon's standard damage is multiplied by the value given in Table 30. Then Strength and magical weapon bonuses are added.

Backstabbing does have limitations. First, the damage multiplier applies only to the first attack made by the thief, even if multiple attacks are possible. Once a blow is struck, the initial surprise effect is lost. Second, the thief cannot use it on every creature. The victim must be generally humanoid. Part of the skill comes from knowing just where to strike. A thief could backstab an ogre, but he wouldn't be able to do the same to a beholder. The victim must also have a definable back (which leaves out most slimes, jellies, oozes, and the like). Finally, the thief has to be able to reach a significant target area. To backstab a giant, the thief would have to be standing on a ledge or window balcony. Backstabbing him in the ankle just isn't going to be as effective.