We'll end our look at "beyond the basics" situations and dive right into the damage a sneak attack does as well as go over the number of sneak attacks you can do.
Creatures become susceptible to sneak attacks when flanked because they must divide their attention between two or more opponents whose relative positions make it difficult to block or dodge their attacks. The situation is something like dealing with an unseen foe, but isn't quite as severe.
To flank an opponent, two allies must be on opposite sides of that opponent, and they both must threaten the opponent (Chapter 8 in the Player's Handbook has some handy diagrams that explain flanking). You threaten an opponent when you can make an armed melee attack against that opponent. You're "armed" when you use a manufactured weapon, natural weapon, the Improved Unarmed Strike feat, or the monk's unarmed strike ability. You don't actually have to have a weapon that can hurt an opponent to threaten that opponent. If you and your buddy have no silver weapons but find yourselves on opposites sides of a werewolf, you still flank the werewolf (but see the final section of this article series).
You can flank with any melee weapon, including a reach weapon, but you cannot flank with a ranged weapon.
You get a flanking bonus from any ally your foe can see (and who is in the correct position to flank). If your foe can't see you, you don't provide a flanking bonus to any ally. You literally cannot flank a blind creature; however, a blind creature loses its Dexterity bonus to Armor Class against your attacks (so you can sneak attack it), and you get a +2 to attack it to boot. Creatures with the blindsight ability effectively "see" within blindsight range and can be flanked.
The improved uncanny dodge class ability can prevent a creature from being flanked (see the next section).
Uncanny Dodge and Sneak Attacks
The uncanny dodge class ability is just about the nastiest sneak attack breaker in the game. Only immunity to critical hits offers more absolute protection against sneak attacks. So, uncanny dodge gets a section in the article all to itself.
The uncanny dodge ability allows a flat-footed creature to retain its Dexterity bonus to Armor Class (if any) and it foils sneak attacks when in does so.
The uncanny dodge ability also allows a creature to use its Dexterity bonus (if any) against unseen foes, so an unseen foe must find some other way to make sneak attacks against creatures with this ability.
Uncanny dodge does not allow a creature to keep its Dexterity bonus to Armor Class (if any) when it physically cannot move. If you're grappled, held, helpless, incapacitated, pinned, or stunned, you lose your Dexterity bonus to Armor Class. If you're attacked while climbing, you also cannot use your Dexterity bonus to Armor Class. Uncanny dodge doesn't allow you to retain your Dexterity bonus to Armor Class in any of these cases.
The improved uncanny dodge class feature can keep a creature from being flanked, except by a rogue who is four or more levels higher than the target. An attacker with sufficient rogue levels can flank the defender simply by having an ally opposite the defender, if that ally cannot flank the defender himself, provided that the defender can see or perceive your ally (see the section on flanking). In such a case, the ally gets no benefit for being in a flanking position, but the rogue gets full benefits.
When determining who can flank whom, start by counting the target's levels, and count only those levels in classes that provide the uncanny dodge class feature. Then count up the attacker's levels, counting only levels in classes that provide the sneak attack class feature. For example, a 10th-level rogue could not flank a 5th-level barbarian/5th-level rogue but the same character could flank a 5th-level barbarian/5th-level bard. Likewise, a 7th-level rogue/7th-level assassin could flank a 5th-level barbarian/5th-level rogue.
Damage from Sneak Attacks
The bonus damage from a sneak attack is expressed as extra dice and it is not multiplied with a successful critical hit, or when an attack otherwise gets a damage multiplier. For example, a rogue charging with a mounted lance can make a sneak attack, but the damage multiplier for the mounted charge doesn't apply to the sneak attack.
A successful sneak attack increases the damage dealt. When you make a sneak attack against a foe with damage reduction, roll the sneak damage and add it to the damage from the hit before applying the effects of damage reduction.
Sneak attack damage is always the same type of damage as the weapon used to make the sneak attack. For example, if you make a sneak attack with a sword (a slashing weapon), all the damage from the sneak attack is slashing damage (also see the Spells as Sneak Attacks section in Part Four).
Number of Sneak Attacks
Provided it is possible for you to make a sneak attack at all, you can make multiple sneak attacks when you use the full attack action. For example, if you have a higher initiative result at the beginning of an encounter, your foe is flat-footed and every attack you make is a sneak attack. The same is true if you flank your foe.
Anything that allows you to make extra attacks during the full attack action gets you extra sneak attacks as well: fighting with two weapons, the haste spell, and the monk's flurry of blows are the most common ways of getting extra attacks.
Remember the earlier note about invisibility effects, however. If you're relying on invisibility to set up a sneak attack, you'll only have the effect for the first attack you make during your turn. You'll still get all your extra attacks, but only the first will be a sneak attack. You don't have this problem if you're using a greaterinvisibility effect.
Coming in Part Four of All About Sneak Attacks
Skip goes over volley type attacks, spells, and some other fun stuff.
About the Author
Skip Williams keeps busy with freelance projects for several different game companies and has been the Sage of Dragon Magazine since 1986. Skip is a co-designer of the D&D 3rd Edition game and the chief architect of the Monster Manual. When not devising swift and cruel deaths for player characters, Skip putters in his kitchen or garden (his borscht gets rave reviews).