Two other "beyond the basics" situations that come up with sneak attacks are unseen opponents and immobilization. Let's take a look at these topics now.
Facing an Unseen Opponent
To properly defend itself in combat, a creature must be able to see its foe, or use some ability acute enough to substitute for sight, such as the blindsight special quality (or the uncanny dodge ability; the section on uncanny dodge section is in Part Three).
When facing a totally concealed foe, a creature is denied Dexterity bonus (if any) to Armor Class and the attacker gets a +2 attack bonus as well.
Perhaps the most common form of total concealment is the invisibility spell. A regular invisibility effect is broken when you attack. If you begin your turn under such an effect and you're making multiple attacks, you'll be invisible only for the first attack and your opponent will be denied Dexterity bonus to Armor Class (if any) against that first attack.
Just about everyone has total concealment against a blinded creature, and total darkness gives everything total concealment against foes that don't have darkvision. Remember however, that concealment cuts both ways. Sneak attacks aren't possible when the target has any concealment whatsoever.
Some special qualities and skills allow creatures a limited ability to locate unseen foes. The scent special quality and the Spot and Listen skills all give some chance of figuring out exactly where an unseen foe lurks. So can cruder means, such as scattering sand or flour all over a dungeon floor when you suspect there's an invisible foe nearby. These measures allow you to locate an unseen foe, and possibly attack her, but they don't negate the foe's total concealment, so they won't keep you from being sneak attacked. It's not enough to know where your foe is. You've got to know when and where the attack is coming.
On the other hand, it's only total concealment that interferes with Dexterity bonuses to Armor Class. Anything that knocks down total concealment to a lower degree makes any Dexterity bonuses to Armor Class available again. A spell such as see invisibility or true seeing robs an invisible foe of its total concealment, but only for the creature using the spell; the spell user could then use other means to render the invisible foe at least partially visible to allies, however. Splattering an invisible foe with a little flour or paint reduces or eliminates an invisible creature's total concealment, at least for a little while, as does a trusty glitterdust or faerie fire spell.
The blindsight ability allows its user to discern any unseen creature within range just as though the unseen creature was fully visible (provided the creature with blindsight has line of effect to the concealed creature). A creature with blindsight thus retains its Dexterity bonus to Armor Class (if any) against an unseen foe and blindsight also negates most kinds of concealment. This means that you can't sneak attack a creature with blindsight unless you have it flanked or catch it flat-footed. Also, a creature with blindsight can ignore any concealment a foe has when making a sneak attack of its own.
A blink spell provides the user with some degree of concealment -- and foils sneak attacks -- when the attacker cannot see ethereal opponents. (Both the see invisibility and true seeing spells reveal ethereal opponents).
An attacker that can see, but not affect, ethereal opponents still has a miss chance (20%) against a target using blink because the foe might be ethereal when the attack strikes; however, this does not arise from concealment and does not foil sneak attacks (though a miss is still a miss).
When an attacker is using blink itself, it has a 20% miss chance (because it sometimes finds itself ethereal when its attack strikes home). This miss chance also does not interfere with the attacker's sneak attacks. In fact, a blinking attacker strikes as an invisible creature, and its foes are denied Dexterity bonus (if any) to Armor Class and that makes sneak attacks possible. If the blinking attacker's target can see ethereal opponents, that foe retains Dexterity bonus (if any) to Armor Class and cannot be sneak attacked unless flat-footed or flanked. Because a blinking attacker's "invisibility" is actually etherealness, blindsight does not allow a foe to retain its Dexterity bonus against the attacker, and blindsight does not reduce the miss chance for attacks against the blinking combatant.
When you can't move, you can't use your Dexterity bonus (if any) to Armor Class, and you can be sneak attacked even when you're not flanked or caught flat-footed.
Any of these conditions keep you from using your Dexterity bonus to Armor Class: grappled, held, helpless, incapacitated, pinned, or stunned. Immobility is one time when the uncanny dodge ability doesn't foil a sneak attack (see the section on uncanny dodge).
Grappling is worth a special note. When you're grappling, you lose your Dexterity bonus to Armor Class (if any) against any foe that you are not grappling, and that's true no matter who started the grapple -- you're just as vulnerable if you initiate a grapple as you are when a foe grapples you. You retain your Dexterity bonus to Armor Class, however, against a foe you are grappling. So, if someone grabs you, you can't sneak attack that foe, but your buddies could.
When you're climbing (ascending or descending a vertical surface or a slope too steep to walk up) you cannot use your Dexterity bonus to Armor Class, which makes you vulnerable to sneak attacks (even if you have uncanny dodge).
Being entangled impedes your movement and reduces your effective Dexterity score, but it does not make you vulnerable to sneak attacks.
Coming in Part Three of All About Sneak Attacks
Take a look at a flanked defender, uncanny dodge, and a couple of other topics.
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).