You can find general rules for interactions between magical effects in several places. Key pieces of text include the section entitled Combining Magical Effects on page 171 in the Players Handbook, the text on spell schools on page 172 in the Players Handbook, and the discussion of spell descriptors on page 174 in the Players Handbook.Rules of the Game: Reading Spell Descriptions also deals with this topic.
Some of the most important interactions between magical effects arise when one effect blocks or negates another effect. Unfortunately, the general rules for magical interactions don't cover these effects very well. Instead, you must look at the descriptions for the individual effects before you can resolve the interaction. This week, we'll take a look at a few sample interactions that illustrate some principles you can use when considering magic that interferes with other magic.
Understanding the dispel magic spell provides a good basis for understand how antimagic effects work in general. This section provides a summary of the dispel magic spell description along with some additional commentary. Everything noted here also applies to the greaterdispel magicspell unless noted otherwise. Dispel magic defeats spells and spell-like effects. Everything here also applies to spell-like effects unless noted otherwise.
You can cast dispel magic three different ways (and that alone makes it an unusual spell): As a targeted spell, as an area spell, or as a counterspell. The previous two installments in this series dealt with counterspells, so let's take a look at dispel magic's other two functions.
As a Counterspell Effect
As when casting dispel magic as a counterspell, you must make a caster level check with a DC of 11 + the subject spell's caster level to end the subject spell. When using the dispel magic spell, your maximum bonus for the caster level check is +10. When using the greater dispel magic spell, your maximum bonus for the caster level check is +20.
As a Targeted Effect
When casting a targeted dispel magic, you aim the spell at a creature, object, or spell. You must follow all the rules for selecting a target for the spell -- that is, you must be able to see or touch the target (see page 175 in the Player's Handbook and Rules of the Game: Reading Spell Descriptions. Targeting a creature or object is pretty straightforward. Targeting a spell, however, can prove tricky. If the spell you're targeting has a visible or tangible effect, you can select the target just by looking at it or touching it, as appropriate. If the spell you target is intangible, things get a little tougher.
A detect magic spell can determine the location of the target spell's magical aura, and you reasonably can assume that locating the spell's aura with detect magic is sufficient to target the spell with dispel magic. The DM might also allow you to target a specific spell with dispel magic when you can surmise what the spell is. For example, the barbarian in your group enters a rage and then abruptly freezes in place, not attacking. You might sensibly work out that the character is the subject of a hold person or hold monster spell, and you could target that spell with dispel magic without first resorting to detect magic.
A targeted dispel magic affects only the target, not other creatures, objects, or spells nearby. If the target is an object or creature, the dispel magic has a chance to end every spell that is currently operating on that object or creature, as noted in the spell's description. A dispel magic targeted on a creature does not also affect the creature's equipment, and a dispel magic targeted on a single object in a creature's possession does not affect the creature itself or any other objects in its possession. It's worth pointing out here that a creature and its equipment usually are treated as one entity when the creature receives a spell. For example, when a creature receives a displacement spell, both it and its equipment are displaced. Exceptions to this general rule abound, and dispel magic is one of them.
When you aim a targeted dispel magic spell at a particular spell, only that spell is subject to dispelling. This can be very helpful when you wish to free an ally of one detrimental spell without dispelling any beneficial spells the character has received.
When you select an object as the dispel magic's target, you can end every spell or spell-like effect currently operating on the object. If the target object is a magic item, you can make a caster level check to suppress all the item's magical powers for 1d4 rounds, as noted in the dispel magic spell description. An item's nonmagical properties remain unaffected by dispel magic. A +1 longsword suppressed by a dispel magic spell remains a masterwork longsword.
If the target object is a magic item that also has received one or more spells, you have a chance to end each spell currently operating on the item and a chance to suppress all the item's magical abilities. The spell description doesn't make this point clear, but it's the easiest way to handle things. Dispel magic can't suppress an artifact's magical properties, but it can end spells an artifact has produced.
Aiming a targeted dispel magic at a summoned creature proves similar to aiming the spell at a magic item. The spell has a chance to banish the summoned creature, as noted in the spell description (and in the notes on the summoning subschool on page 173 in the Player's Handbook). If the summoned creature also has received one or more spells, you have a chance to end each spell, plus a chance to banish the summoned creature. If a single summoning effect has brought forth multiple creatures and you target your dispel magic spell on one of them, you can banish only the creature you have targeted.
As an Area Effect
Instead of casting a targeted dispel magic (or using the spell as a counterspell), you can cast the spell as an area spell that fills a 20-foot burst.
An area dispel can't suppress magic items, but it can remove ongoing spells from creatures or objects. For each creature within the burst that has received one or more spells, you make a caster level check against the spell with the highest caster level. If that check fails, you make checks against progressively weaker spells until you dispel one spell or fail all your checks against the spells affecting that subject. Once the area dispel magic removes one spell from a subject, it has no further effects on that subject.
An area dispel magic also ends spells operating in the same area as the burst. If the burst covers the subject spell's point of origin, a successful caster level check from you negates the whole effect, even if the burst does not cover the subject effect's whole area. See page 175 in the Player's Handbook and Rules of the Game: Reading Spell Descriptions for discussions of a magical effect's point of origin. If the dispel magic's burst merely overlaps the subject spell's area without covering the spell's point of origin, a successful caster level check from you negates only the portion of the subject spell that the burst covers.
When the burst from an area dispel magic covers two or more summoned creatures, make a single caster level check. If the check succeeds, you banish each creature the burst covers. If a summoned creature also has received one or more spells, your area dispel has a chance to remove one spell (as noted previously) and a chance to banish the summoned creature.
A targeted or area dispel magic can affect only a spell that is currently operating. When a spell has an instantaneous duration, it can't be dispelled because the magical effect is already over before the dispel magic can take effect.
Some spells aren't subject to dispel magic, as noted in their descriptions (for example, wall of force).
A dispelled spell ends as if its duration had expired. Usually, this means that the spell ends immediately. Be alert for spells that remain for awhile after they expire (for example, the fly spell).
Some spells or groups of spells negate each other. For example, haste and slow counter or dispel each other, and the darkness spell can counter or dispel any spell with the light descriptor, provided the subject spell is of an equal or lower level.
When two spells counter or dispel each other, either spell can function as a counterspell against the other, as noted in Part One.
The rules aren't very clear about what happens when opposing spells dispel each other. In general, you can rule that the two spells negate each other. When two opposing spells have targets, one spell can remove the other when aimed at the same target. Treat the second spell just like a targeted dispel magic except that no caster level check is required and only the opposing spell is negated. For example, if a creature has received a haste spell, targeting a slow spell on the same creature automatically removes the haste effect, leaving the subject neither slowed nor hasted. When two opposing spells can affect multiple targets, they only negate each other when they share the same targets. For example, when you cast a slow spell on six enemies and two of them have received haste effects, the spell removes the two haste effects, leaving the other four targets subject to the slow spell's normal effects.
When two opposing spells have areas, one spell can remove the other when aimed at the same area. If the second spell's area covers the first spell's point of origin, both spells are completely negated (no caster level check is required). If the second spell's area of effect merely overlaps the first spell's area without covering the spell's point of origin, the two spells negate each other only the area where the areas overlap.
Light and Darkness Descriptor Spells: Most spells with the light and darkness descriptors have target entries. This means that you must aim a spell with the darkness descriptor at the same target as a spell with the light descriptor if you want to use the former spell to dispel the latter spell. Spells with the light and darkness descriptor have an unusual property, however; they cause their targets to emit light or darkness and when cast on moveable objects, the illuminated or darkened areas also are mobile.
Whenever two such areas are aimed or moved so that the areas they affect overlap, the two spells usually temporarily suppress each other. This means that the usual light conditions prevail in the area of overlap. For example, a daylight spell makes a dim chamber bright with light. A darkness spell fills the same room with shadows. If the two spell effects are allowed to overlap, there will be an area of dim light in the area of overlap bordered on one side (the daylight side) by bright light and on the other (the darkness side) by shadowy light. In this case, the two spells otherwise do not affect each other. If the two effects move away, both spells work again.
It's also possible that the higher level spell keeps working and the lower level is suppressed. For example, when you cast a darkness spell on an object and then move the object so that the darkened area covers the area where a light spell provides illumination, the lower level light spell stops working until someone moves the darkness effect away.
Though this discussion of mobile spell effects pertains to spells with the darkness and light descriptors, you might find it helpful when dealing with other mobile spell effects as well.
That wraps up our present look at magical oddities. We've covered a fair amount of ground this month, and I hope you're now in a better position to deal with these topics when they arise in your games.
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.