The section on invisibility in Chapter 8 of the Dungeon Master's Guide contains a great deal of information about invisibility's ramifications in combat. Take a look at the highlights.
Dealing With Invisibility in Combat
Several special qualities, such as blindsense, tremorsense, and scent, allow you to locate unseen creatures (though you must be fairly close to the creature to locate it with scent).
You can use a Spot or Listen check to locate a creature you cannot see, though doing so is very difficult indeed (see Spotting, Listening, and Pinpointing).
Because you cannot see the creature, your attack has a 50% miss chance. The Dungeon Master's Guide says the DM can waive or reduce the miss chance when the target is particularly large and slow. As a rule of thumb, you can reduce the miss chance by 5% for every size category the target is beyond Large. If the target is size Huge or bigger, also reduce the miss chance 5% for every 5 feet that the creature's current speed is below 30 feet. Also, reduce the miss chance by 20% if the attack is aimed more or less at the creature's center, or if the creature is using the squeezing rules (see page 29 in the Dungeon Master's Guide) to move into a locale narrower than its space. Finally, reduce the miss chance another 10% if the creature is particularly blocky or massive for its size category. All the reductions stack, but a miss chance cannot be less than 0. For example, a black pudding is a Huge creature with a speed of 20 feet. As an ooze, it's just a big blob, and both exceptionally blocky and massive for its size category. Attacking an unseen black pudding entails a miss chance of only 20% (base 50% -10% for size Huge, -10 for speed, -10 for mass). The example black pudding has a space listing of 15 feet (three squares by three squares). If the attack is aimed at the pudding's center square, the miss chance is 0%.
Any attack that depends on hitting a foe in a particular place or in a particular way doesn't work against an unseen foe. Sneak attacks and bonus damage from the favored enemy class feature falls into this category. The DM might decide to include others as well.
If a spell has a target or targets entry, you must see or touch your target to aim the spell at it. Even if you know where your unseen target is, you still can't aim a targeted spell at it if you don't see or touch it.
Spotting, Listening, and Pinpointing
As noted earlier, you can use a Spot or Listen check to locate something that's invisible.
If you can't discern an invisible thing visually, how on earth do you spot it? Well, the rules aren't clear on that point. However, invisible things often leave visible clues to their presence. Exactly what forms these clues take depend largely on what the invisible thing is and what its surroundings might be like. For example, an invisible creature walking around in a dungeon might leave the occasional footprint or set dust motes swirling in the air. A creature that has been invisible for a long time might even pick up enough dust and debris that it develops a faint outline. Also, some invisibility effects aren't perfect. Perhaps an invisible thing creates the faintest shimmer or distortion in the air, or casts a really feeble shadow. Such phenomena might prove very difficult to detect, but perceptive individuals might see them and recognize them for what they are.
Spot Check DCs
Considerable confusion often arises regarding how difficult a Spot check to notice or locate an invisible thing is; the latter is much harder than most people realize. That's because the basic Spot DCs noted in the Dungeon Master's Guide are for merely noticing that there's something unseen somewhere within 30 feet. The DC for actually pinpointing an invisible thing's location so that you know where to aim an attack is 20 points higher. The table below shows the Spot DCs for various kinds of invisible things. The DCs given here are higher than those shown in the Player's Handbook's glossary (pages 309-310), and they match the numbers given in the Dungeon Master's Guide glossary (page 295).
According to the Spot skill description, it doesn't take an action to make a check to notice or locate an invisible thing when you first have a chance to do so. After that, however, it takes a move action to spot something you failed to see earlier. In this case, however, I recommend that you make spotting an invisible creature a free action each round, at least when there's an active invisible creature (see below) involved.
When a Spot check result is too low to locate an invisible creature, but high enough to notice that it's within 30 feet, the character making the check notices the creature (see below). It's best to make the Spot check secretly so that players cannot be sure if they're actually dealing with invisible foes.
Spot DC to Notice: If the check is successful, you merely know there's something unseen within 30 feet of you. If the invisible thing is more than 30 feet away, you cannot notice it with a Spot check. According to the rules, any time you make a Spot check you take a -1 penalty on the check for every 10 feet of distance between you and what you're spotting.
You must repeat the check each turn to keep track of the unseen thing.
Spot DC to Locate: If the check is successful, you know exactly where the invisible thing is (you have pinpointed its location), including what square or squares on the battlefield it occupies. Apply the penalty for distance to this check (-1 per 10 feet).
You must repeat the check each turn to keep track of the unseen thing. I recommend you make this a free action each round.
Active Creature: For purposes of spotting an invisible creature, it is "active" when it has moved (that is, gone from one place on the battlefield to another) during its last turn.
Living Creature Holding Still: A living creature has Constitution, Wisdom, and Charisma scores. A creature is holding still if it has not moved during its last turn.
Inanimate Object: An object that's sitting by itself. If an object is in motion but staying in place (such as a swinging pendulum or a spinning wheel), use the Spot DC for a living creature holding still. If the object is actually moving across the battlefield (such as an iron ball rolling along or a pendulum swing across two or more squares) use the DC for an active creature.
Unliving Creature Holding Still: An unliving creature has Wisdom and Charisma scores, but no Constitution score. It is holding still when it is not moving, as noted above under Living Creature Holding Still.
Completely Immobile Creature: In this case, complete immobility refers to a creature that is being careful not to move a muscle. It can be a creature that is under paralysis, a hold spell, or some other effect that utterly prevents it from acting, so that it just sits in place like an inanimate object. A sleeping creature might be considered completely immobile if its slumber is deep and untroubled (as it would be if the creature is under a magical sleep effect). A creature sleeping fitfully should be considered holding still.
Invisibility and Hiding
As noted in the description for the Hide skill, you gain a +20 bonus on Hide checks if you're moving and +40 on Hide checks if you're not moving.
To make a Hide check at all, you need some sort of concealment or cover, and that applies even when you're invisible and the creatures trying to spot you can't see invisible things. Invisibility gives you total concealment, but spotting something invisible carries its own Spot DCs and you can't make yourself harder to see without a little extra help from your surroundings.
When making your Hide check, apply all the modifiers that normally apply to the check (such as Armor Check penalties and penalties for your movement). Perceptive readers will note that you're effectively paying a double penalty for moving here because the bonus for being invisible is lower and you take a Hide check penalty for that movement as well. That, however, is the nature of invisibility in the D&D game. Any movement makes you easier to spot while you're invisible, whereas your speed makes it harder for you to hide and the effect gets worse the faster you go.
As noted in the Dungeon Master's Guide, you can use hearing to notice an invisible creature (inanimate objects don't make any noise).
To resolve an attempt to hear an invisible creature, have the listener make a Listen check opposed by the invisible creature's Move Silently check (if the invisible creature has no Move Silently ranks it makes an untrained check).
The table below is a modified version of the one included on page 295 of the Dungeon Master's Guide. It includes Move Silently penalties for creature's movement (taken from the Move Silently skill description), and modifiers for barriers. Other Move Silently modifiers (such as the armor check penalties and modifiers for the surface the invisible creatures moves across) are not included.
According to the Dungeon Master's Guide, a Listen check to notice or locate an invisible creature is a free action each round.
Listen DC to Notice: If the check is successful, you merely know there's something unseen somewhere near you, but you don't know where or what direction.
You must repeat the check each turn to keep track of the invisible creature.
Listen DC to Locate: If the check is successful, you know exactly where the invisible thing is (you have pinpointed its location), including what square or squares on the battlefield it occupies.
You must repeat the check each turn to keep track of the invisible creature.
Moving at Half Speed: Use this modifier if the invisible creature is moving at all and if the distance it moved during any single action during its last turn was equal to or less than half its current speed. If surface conditions limit its movement, use this modifier only if the creature moves no more than half the distance in speed that the conditions allow. For example, if the creature has a speed of 40, it's moving half speed if it moves 20 feet or less during any single action. If the creature is moving over terrain that hampers its movement, however, it can move only 20 feet with a single action and is considered moving at half speed only if it moves 10 feet or less during one of those actions.
Moving at Full Speed: Use this modifier if the invisible creature moves at more than half speed, as defined above.
Behind a Door: Use this modifier for any fairly thin barrier that's no thicker or stronger than an iron door.
Behind a Stone Wall: Use this modifier for barriers thicker or stronger than an iron door.
Other Ways to Deal With Invisible Foes
You don't have to rely on Spot or Listen checks, or on magic, to locate and attack an invisible foe. Here are some other options.
Probing an Area: You can grope or probe about to find an invisible creature as a standard action. To do so, pick two 5-foot squares that are both adjacent to each other and within your melee reach; if you have a natural reach of more than 5 feet, or a reach weapon, you can probe squares that aren't adjacent to you.
If the squares you probe contain anything you can't see, you make a melee touch attack (or attacks if there is more than one thing you can't see). There is a 50% miss chance on the touch attack. If an attack succeeds, you deal no damage but you have successfully pinpointed the invisible thing's current location. (If the invisible thing moves, you don't know where it is anymore.)
Because you have to use a standard action to probe for unseen things, you usually can't do anything about unseen foes you locate (unless they're foolish enough to stay put until your next turn), but you can use a free action to relay the foe's location to your allies. One effective tactic for a group is to have one member probe while everyone else readies actions to attack whatever you find. They can also simply delay until the probing character finds something. See page 160 in the Player's Handbook for information on readying and delaying.
Attacked by an Unseen Foe: If a foe you cannot see hits you with a melee attack and is adjacent to you at the time, you know the foe's location. For this reason, smart foes move right after they attack; even a foe that has made a full attack can move after attacking by taking 5-foot step (provided it has not already moved during its turn).
When an unseen foe hits you with a melee attack from more than 5 feet away, you know the general direction from which the attack came and that the attack came from more than 5 feet away, but you do not know the attacker's location.
Looking For Tracks: Unseen creatures leave tracks, and you can track them using the normal tracking rules. Footprints in sand, mud, or other soft surfaces can give clues to an invisible creature's location.
If the tracks are very clear and the surface that carries them is fairly smooth and unsullied by debris or other tracks, you can locate a creature you cannot see by looking at its visible tracks; tracks aren't visible, however, unless you can see the surface that holds them. For example, it's no good looking for an unseen creature's tracks if the battle is taking place during a blizzard and you're not entirely sure where the ground ends and sky begins. If the battle is taking place in a bright morning when the whole battlefield is covered in fresh snow, however, an unseen creature's tracks probably will betray its location, at least during the first few rounds of a fight (before all the snow becomes thoroughly trampled).
Surfaces or conditions that don't leave clear tracks still might give you a bonus (the DM can decide how big) in Spot checks to notice or locate unseen creatures. You might get a Spot bonus in areas covered with tall grass, undergrowth, dust, or running water (assuming the unseen creature is wading and not submerged; see next section).
Underwater: An invisible thing underwater displaces water, and that creates a visible space that reveals the invisible thing's location. The DM might apply this effect under other circumstances as well, such as areas of heavy smoke, areas draped with lots of dangling things (such as vines, cloth, skeins of rope), heavy precipitation, or the like.
Marking an Invisible Creature: Since a visible object stays visible when an invisible creature picks it up (at least until the invisible creature tucks the object into its clothing), you may make an invisible thing visible (or at least reveal its location) by dousing it with something visible. My own favorite device for doing this is a bag packed with about a pound of flour. You could just as easily use ink or paint.
Toss the bag of flour just like a splash weapon. A direct hit leaves an invisible creature smeared with flour, which reveals the creature's location. An invisible creature caught in the flour's splash effect can attempt a Reflex save (DC 20) to avoid getting covered with flour. A creature can shed its outer clothing (at least a full-round action) and be rid of the flour. Otherwise, it must bathe or wait for the flour to wear off on its own (which takes an hour or two in dry conditions).
Special Qualities and Feats Against Unseen Foes
Creatures with the scent ability can sniff out unseen creatures, as noted in the scent description in the Monster Manual glossary. The blindsense ability reveals unseen things' locations only. Tremorsense reveals unseen creatures' locations, provided that they are in contact with the ground.
The blindsight ability effectively negates invisibility. (The user can deal with unseen things just as though they were visible.)
Anyone with the Blind-Fight feat has an improved chance to hit an invisible creature. Roll the miss chance twice, and the attacker misses only if both rolls indicate a miss. (Alternatively, make one 25% miss chance roll rather than two 50% miss chance rolls.)
That pretty well covers invisibility. Next week, we'll look at the basics of incorporeality.
About the Author
Skip Williams keeps busy with freelance projects for several different game companies and was the Sage of Dragon Magazine for many years. 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 (rabbits and deer are not Skip's friends) or works on repairing and improving the century-old farmhouse that he shares with his wife, Penny, and a growing menagerie of pets.
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