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Backstab is an ability that allows attacks made while concealed and behind a target to perform additional damage. The additional damage is substantial enough to often kill targets in a single blow. This ability is available to thieves (except swashbucklers), and stalkers.

Mechanics

In order to attempt a backstab, the character must be:

Any attack made while these conditions are met will be treated as a backstab attempt. Regardless of whether the attempt is successful or not, the attacker will immediately become visible. If the attack roll is successful, the target will suffer a multiple of the weapon's normal damage.

If the attacker is dual-wielding, the backstab attempt will be made with the weapon in the main hand. If that weapon isn't suitable for backstabs, the attack may still succeed but it will only result in normal damage. Since the first attack usually breaks concealment, the character's APR is not relevant.

Backstabbing while invisible will ignore the enemy's Dexterity bonus to armor class.[1]

Will the party get backstabbed?

Any enemy with a backstab multiplier (e.g. a character with Thief/Stalker levels) who attacks the party from either invisibility or hiding will attempt to backstab the party (one can easily test this by simply casting invisibility on any enemy with actual Thief levels). This means that enemies do not require positioning like players do to perform backstabs.

While your average Mugger (a lot of whom use ranged weapons, that can't backstab) probably won't try to hide-in-shadows or go invisible, actual Shadow Thieves, assassins and other kinds of more skilled enemies are scripted to either try to hide (if no enemy is nearby) or, more commonly, drink Potions of Invisibility or use the MAGE01.ITM's invisibility at the start of combat.

Some rogues have the HIDE.BCS script that simply checks if the creature is invisible or not, and if not, it tries to Hide, using the available Stealth percentage. Most Hide in Shadow and Move Silently skills assigned to thieves are quite marginal. Thus, attaining a hidden state is typically achieved by the AI through invisibility items or consumable potions.

Some examples of enemies (ie it's not an exhaustive list) who might try to backstab the party - mostly in Shadows of Amn portion of BG2EE are:

Enemies immune to backstab

This is a (mostly complete) list of enemies immune to backstab. If an enemy isn't listed here, odds are it's vulnerable to backstabs (keep in mind that monsters that ignore invisibility like most Liches and Demons might seem immune at first, but they aren't):

General creature types:

Specific enemies:

Primary enemies:

Backstab eligible weapons

Backstabs can only be performed with fists or melee weapons that a pure Thief would be able to use:

Even if a weapon falls into one of the above categories, it may not be used for backstabbing if:

Any spell-conjured melee weapon is eligible for backstabbing, regardless of its apparent weapon class. This includes weapons created by spells such as Spiritual Hammer and Black Blade of Disaster.

Worthy of note, Ogre form from Polymorph Self and Iron Golem form from Shapechange deal significantly more damage and can be used to backstab.

Slayer Form, which all protagonists get, can also backstab.

Backstab damage formula

((weapon damage + damage bonuses) × multiplier + strength bonus) x critical multiplier where:

For most characters, the backstabbing weapon with the most damage potential is the upgraded Staff of the Ram, which does 1d6 +12 crushing + 1d4 piercing points of damage per hit. A Mage / Thief, however, has access to the Black Blade of Disaster which can do 2d12 +5 (and +5 more from Grandmastery in Longswords in the EE) points of damage per hit, Ogre form from Polymorph Self which does 4d6 + 1 points of damage and Iron Golem form from Shapechange which can do 4d10 points of damage.

Backstab success chance

Since a backstab occurs with a successful hit, success chance can be increased by improving THAC0. See the general article on THAC0 for ideas on how this attribute can be improved. Taking the Single Weapon or Two-Handed Weapon proficiency improves the critical hit chance, ensuring a 10% chance to hit. Since backstab is usually tried from Stealth / Invisibility (unless using Assassination HLA), you also gain a +4 THAC0 bonus.

As members of the warrior group, Stalkers are much less likely to suffer from THAC0 issues than thieves. See the class page for thieves for ideas on how to improve their THAC0. In terms of general advice (applicable to both), be wary when dual wielding since the main-hand weapon will suffer a THAC0 penalty until the character is specialized (2 points) in two-weapon fighting. In the late game, a weapon that increases Strength, like Angurvadal or Crom Faeyr might compensate that even if as a plain Thief you only have access to one proficiency point in that style. Also, consider playing as an Elf, since they receive a +1 to-hit racial bonus when using short swords and long swords.

Some effects, mostly from spells, allow an attacker to automatically hit the enemy, thus guaranteeing a successful backstab attempt. These effects include:

Additional backstab opportunities

Instead of using Hide-in-Shadows, a thief can use Invisibility to create a backstab opportunity. The advantage to this method is that it can be done while in the direct line of sight of enemies while in the midst of combat. Various wizard spells would work for this purpose, as would drinking a Potion of Invisibility. See the section on Backstab#Invisibility later in this article for a complete list of items and spells.

The high-level ability Assassination allows for a full round of attacks using the backstab multiplier (without the need for concealment). Increasing APR, such as with the Improved Haste spell and wielding Belm and/or Kundane, is the key to getting the most out of this ability. Assassination is often best used after a time trap triggers to ensure that all attacks automatically hit, each one of them a backstab.

The Mislead spell allows characters to attack without breaking concealment. As a result, every attack they make (including with the offhand) are treated as backstabs as long as they stay behind their target. While this option is only directly available to the Mage / Thief and the Fighter / Mage / Thief classes, any thief with the Use Any Item high level ability can use scrolls of Mislead as well.

Backstab multiplier table

Level Thief/Bounty Hunter Assassin Stalker Shadowdancer
1-4 ×2 ×2 ×2 -
5-8 ×3 ×3 ×2 ×2
9-12 ×4 x4 ×3 ×3
13-16 ×5 ×5 ×3 ×4
17 ×5 ×6 ×4 ×4
18-20 ×5 ×6 ×4 ×4
21-24 ×5 ×7 ×4 ×4
25+ ×5 ×7 ×4 ×4

Invisibility

Items:

Wizard spells:

Druid/Shaman spells:

See also

Visuals

Gallery:

Slideshow:

Mod content

Mods icon This section is about unofficial content that is only available via fan-made mods.

Mods:

The Tweaks Anthology mod offers an optional backstab component under the "Rule Changes" section, titled Make Certain Creatures Immune to Backstab/Sneak Attack (Luke).

Technically speaking, a rogue can backstab/sneak attack only living creatures with discernible anatomies. As a result, this component makes sure all those creatures that lack vital areas to attack are immune to backstabs/sneak attacks. This includes the following creatures:

The Rogue Rebalancing mod makes some adjustments to the backstab modifiers depending on the rogue kit. During gameplay, thieves, assassins and such perform backstabbing on a more frequent basis against the party than in the unmodified game.

The Sword Coast Stratagems mod revises almost all thief and eligible kits to be scripted to prioritize backstabbing attacks in combat. These will be attempted everywhere hostile thieves and assassins are encountered. Thieves in general are poor melee fighters, and backstabbing is one of the only special abilities the game engine has to use them effectively. This will be a real threat to the party when their hit points are on the low to moderate side. Plan accordingly.

Vampire creatures in SCS can backstab with their touch attacks, as long as they attack from stealth or if invisible. These creatures' class is changed to Fighter/Thief by the mod.

The Spell Revisions mods summoned Invisible Stalker (BG II - ToB) will Sneak Attack and can backstab opponents with a x2 multiplier. As this creature is always invisible, it gets the modifier on nearly every strike it lands which will be with their 2 Attacks Per Round, 2d6+4 Crushing Damage (Fist +2).

The Tactics for BG2EE mod and the Twisted Rune Hideout component add backstabbing Rune Assassin enemies to the encounter.

The Azengaard mod add backstabbing Rune Assassins to a specific encounter.

The CoM Encounters mod places a group of backstabbing rogues in the Sewers (Slums District).

Gallery:

References