Backstab

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:
* Listed in the game's BACKSTAB 2DA file, these are differentiated as: Thief, Shadowdancer, Assassin, Bounty Hunter and Stalker. 
* Concealed: while typically achieved by use of the Hide in Shadows ability, it can also be achieved through the use of spells, a Potion of Invisibility, or magic items (see the Invisibility section for a complete list). An important benefit of invisibility is that it imposes no armor restrictions.
* Behind the target: in the original Baldur's Gate, a backstab could be initiated from any angle. With Tales of the Sword Coast, backstabbing was adjusted to require the attacker to be within a 90 degree arc behind the target, which carried over to Shadows of Amn and the Enhanced Editions.
* Wielding an appropriate weapon: see the Backstab Eligible Weapons section for a discussion on the eligible weapons.
* The high-level thief ability Assassination allows backstabs without being concealed or behind the target.
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.https://gibberlings3.github.io/iesdp/opcodes/bgee.htm#op20
== Will the Party get Backstabbed?==
Any enemy with a backstab multiplier (eg a character with Thief 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:
*Aran Linvail if sided with Bodhi.
*Arkanis Gath if sided with Bodhi.
*Brennan Risling, part of a group of adventurers on the second floor of the Den of the Seven Vales - if made hostile.
*Cless Ironeye, Shadowdancer member of the Vagrant Blades.
*Ketta at the Guarded Compound. 
*Roger the Fence, if attacked, in the Sewers (Temple District).
*Shadow Thieves in many places, like the Shadow Thieves' Guild Hall and Maevar's Guild Hall, both in the Docks District.
*Embarl, if attacked during while performing a task for Mae'Var.
*Ferric Ironblade will perform backstab attacks as part of Samia's Proposal.
*Eler Had in Gromnir's Hideout.
*Iko, during the Summoned to the Harper Hold quest line. 
*Gaelan Bayle and Arledrian in Gaelan Bayle's Home, if siding with Bodhi.
*Geld Quickblade in the Abandoned Amphitheater forest, part of Rasaad's Journey in BG2EE.
*Alnarow during the final stages of the Mage Stronghold quest in The Planar Sphere.
*Several Tiefling thieves in Watcher's Keep Teleport Maze, including one in Aesgareth's party.
*Dunbar the Fifth (only if Mrs. Cragmoon is reported to the authorities by the party).
*Rune Assassin, during the Solve the "skinner" murders in the Bridge District quest.
*Neb, as part of the Gain the services of Sir Sarles for the temple quest.
*Damien, of the Adventuring Party (Underdark) encounter.
*Drow Assassin, part of the Drow gate guardians before the transition to the Elven Temple in the Kuo Toa in Underdark area.
*Regis from Drizzt's party, if attacked in Chapter Six (but he wields a mace, so won't get a damage modifier).
*A Bounty Hunter (Planar Prison Thief), during the Rescue Raelis and Haer'Dalis from the Planar Prison quest.
*Murderer group in the Battle with Irenicus in Spellhold.
==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:
*Barbarian
*Beholder
*Cornugon
*Demilich (not ordinary liches)
*Deva/Planetar/Solar
*Dragon
*Golem
*Marilith
* Slime/Oozes
*Mist/Wraith (such as Mist/Swamp/Wandering Horrors, Vampiric Wraiths/Mists, Spellhaunts and Slave Wraiths, not the shadowy enemies confusingly called 'Wraiths')
Specific enemies:
* Aesgareth and his entire party
*Bone fiends (Bone Golem-looking demons)
*Specific demons in fight 2-5 of the Black Pits II
*Demon Wraith in the Watcher's Keep Teleport Maze
* Garock/Rock (the two Minotaurs at the Machine of Lum level of Watcher's Keep)
*Guardian Spirit
*Heart Key fight in Watcher's Keep Final Seal level: The Huntress, the unnamed Hive Mother and Ameralis are immune (conversely, Nalmissra, Xei Win Toh and even Y'Tossi are vulnerable to backstabs)
*The Aurumach Rilmani and the Ferrumach Rilmani (Mind Key fight in Watcher's Keep Final Seal level)
*Ka'rashur and his "party" of demons (even the ones that would normally be vulnerable to backstabs)
*Kiser (in Saradush)
*Liches, only two of them: Azamantes and Vongoethe
*Nyalee
*Tahazzar and his "party" of demons (even the ones that would normally be vulnerable to backstabs)
*Velithuu (the Ice Salamander-looking Demons found in the Watcher's Keep Maze level)
*Ferrusk in the Underground River wears the Bloody Bone Plate
Primary enemies:
*The Bhaalspawn: Abazigal, Balthazar, Gromnir, Illasera, Sendai, Yaga-Shura (and even his Lieutenants)
*Demogorgon
*Amelyssan the Blackhearted
*Ravager and its Bone Blades
==Backstab Eligible Weapons==
Backstabs can only be performed with fists or melee weapons that a pure Thief would be able to use:
*long swords
*short swords
*katanas
*wakizashis
*Ninjatōs
*scimitars
*daggers
*clubs
*quarterstaves (including special variants like Staff Spear and Staff Mace)
Even if a weapon falls into one of the above categories, it may not be used for backstabbing if:
*Its usage restrictions exclude thieves. For example the Staff of the Magi is a quarterstaff (a permitted weapon category) but cannot be used for backstabbing since its use is restricted to Mages/Sorcerers.
*Access to the weapon was gained through the Use Any Item HLA.
*Access to the weapon was gained through multi/dual classing
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. 
* Ogre form wields a single-handed Morningstar that deals 4d6 + 1 damage with an additional +6 damage from the 18/00 strength change.
* Iron Golem form uses fists to deal 4d10 damage with an additional +12 damage from the 24 strength change.
Slayer Form, which all protagonists get, can also backstab.
==Backstab Damage Formula==
((weapon damage + damage bonuses) × multiplier + strength bonus) x critical multiplier
where:
*weapon damage is the weapon's physical damage. This includes bonuses from enchantments and supplemental melee damage, but does not include non-melee damage such as elemental damage. For example, the extra +1d4 piercing done by the upgraded Staff of the Ram would be included, but the +1 Cold Damage from Varscona would not.
*damage bonuses are damage bonuses from class kits, weapon specialization, and weapon style bonuses. This also includes the +4 damage bonus whenever we backstab a ranged or unarmed creature (monks and creatures with hands for weapons do not count).
*multiplier is the backstab multiplier. See bottom of the page.
*strength bonus is bonus damage from high Strength.
*critical multiplier is 2 for critical hits, 1 otherwise.
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:
*Sleep (e.g. from Sleep, Power Word Sleep).
*Held (e.g. from Hold Person, Hold Monster, the Priest HLA Implosion).
*Stunned (e.g. from Power Word Stun, Symbol, Stun).
*Time stopped (e.g. from the spell Time Stop or the Rogue HLA Set Time Trap).
*Warrior HLAs Critical Strike and Smite.
==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	Shadowdancer
 	  	  	  	 	
1-4 	×2 	×2 	×2 	- 	-
5-8 	×3 	×3 	×2 	×2 	×2
9-12 	×4 	x4 	×3 	×2 	×3
13-16 	×5 	×5 	×3 	×2 	×4
17 	×5 	×6 	×4 	×2 	×4
18-20 	×5 	×6 	×4 	×3 	×4
21-24 	×5 	×7 	×4 	×3 	×4
25+ 	×5 	×7 	×4 	×4 	×4
==Invisibility==
===Items=== 
*Dagger of the Star 
*Potion of Invisibility
*Ring of Gaxx
*Sandthief's Ring
*The Specter's Ring
===Wizard Spells===
*Invisibility
*Invisibility, 10' Radius
*Improved Invisibility
*Mislead
*Shadow Door
===Druid/Shaman Spells===
*Pixie Dust
==See Also ==
*Stalker
*Thief
*Cleric / Thief
*Fighter / Thief
*Fighter / Mage / Thief
*Mage / Thief
* THAC0
==Visuals==
===Gallery===
Cat familiar backstabs Lesser Basilisk Mutamins Garden.png|Cat familiar performs a backstab on a Lesser Basilisk, with Korax the Ghoul's help.
OG CH 3 Bodhi side 12.png|During Chapter 3 Gorion's Ward is carrying out actions in the Perform Bodhi's Tasks to Receive Her Aid quest, and faces Mook and Arkanis Gath, who backstabs the Ward for quintuple damage.
OG Tiefling Thief Backstab.png|Enemy Tiefling Thief (Aesgareth) in the Watcher's Keep Teleport Maze scores quintuple damage backstab on Jaheira. Lack of Iron Skins was a player mistake.
==Mod content==
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 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).
Category:Class abilities
===Mod gallery===
Damien Backstabbing.png|Damien of the Adventuring Party (Underdark) successfully backstabs the party mage for grievous damage. A Stoneskin would have prevented it.
Backstab Celestial Fury.png|Party Assassin backstabs Chandrilla using the Celestial Fury katana for huge slashing damage. Note that the Full Plate and Packing Steel mod is installed, that provides armor wearing creatures with substantial physical damage resistance, or else the target would be dead.
PC Backstabbed.png|PC backstabbed by Assassin in the Illithid Hideout in the Sewers. Will quaff a potion of invisibility and try again unless revealed or stopped. Also uses the Poison Weapon skill.
Drizzt dying.png|Drizzt Do'Urden is near death and backstabbed by an Elder Vampire in The final battle with Bodhi during Chapter 6.
===Slideshow===
Backstab step A1 - Coran in Cloakwood Mines (BGee).png|Step one - Backstabber cannot be seen, victim can
Backstab step A2 - Coran in Cloakwood Mines (BGee).png|Step two - Backstabber can be seen, victim cannot
Backstab step 1 - Coran in Cloakwood Mines (BGee).png|Step one - Backstabber cannot be seen, victim can
Backstab step 2 - Coran in Cloakwood Mines (BGee).png|Step two - Backstabber can be seen, victim cannot