James Gasik
We don't talk about Pun-Pun
Yeah, I knew that's how it worked in 2e. I suppose there was no way to publish errata in those days outside of in Dragon, and I know the PHB and DMG didn't come out at the same time. Still, it's one of those things that unless the DM mentions it, I wouldn't, by looking at the spell realize that was something it could do.Doesn't look so much "secret" as simply an example of "discovered it's raised often enough to be worthy of printing after the PHB was printed".
The first PHB section seems to be about magic items that happen to be in contact with the effect (ie not like flamestrike or something), the second DMG section seems to be some guidance for the "um, we noticed folks feel like casting this on a specific item should function differently, here's a good ruling we like that doesn't result in a six level drop on the /L9 disjunction spell" type blurb. I may not have the 1e books to reference but I do have the ad&d2e books & those clarify things nicely. Instead of the DMG blurb (I couldn't find it with a quick search) the spell itself in the PHB is clarified to include the secondary edge case itself.
Dispel Magic
(Abjuration)
Range: 120 yds. Components: V, S
Duration: Instantaneous Casting Time: 3
Area of Effect: 30-ft. cube Saving Throw: None
When a wizard casts this spell, it has a chance to neutralize or
negate magic it comes in contact with, as follows:
First, it removes spells and spell-like effects (including device
effects and innate abilities) from creatures or objects. Second, it dis-
rupts the casting or use of these in the area of effect at the instant
the dispel is cast. Third, it destroys magical potions (which are treated
as 12th level for purposes of this spell).
Each effect or potion in the spell’s area is checked to determine if
it is dispelled. The caster can always dispel his own magic; otherwise,
the chance to dispel depends on the difference in level between the
magical effect and the caster. The base chance is 50% (11 or higher
on 1d20 to dispel). If the caster is of higher level than the creator of
the effect to be dispelled, the difference is subtracted from the num-
ber needed on 1d20 to dispel (making it more likely that the dispel
succeeds); if the caster is of lower level, the difference is added to
the number needed on 1d20 to dispel (making it less likely that the
dispel succeeds). A roll of 20 always succeeds and a roll of 1 always
fails. Thus, if a caster is 10 levels higher, only a roll of 1 prevents the
effect from being dispelled.
A dispel magic spell does not affect a specially enchanted item,
such as a magical scroll, ring, wand, rod, staff, miscellaneous item,
weapon, shield, or armor, unless it is cast directly upon the item.
This renders the item nonoperational for 1d4 rounds. An item pos-
sessed and carried by a creature gains the creature’s saving throw
against this effect; otherwise, it is automatically rendered nonopera-
tional. An interdimensional interface (such as a bag of holding)
rendered nonoperational would be temporarily closed. Note that an
item’s physical properties are unchanged: A nonoperational magical
sword is still a sword.
Artifacts and relics are not subject to this spell; however, some of
their spell-like effects may be, at the DM’s option.
Note that this spell can be very effective when used upon
charmed and similarly beguiled creatures. Certain spells or effects
cannot be dispelled; these are listed in the spell descriptions.
Summary of Dispel Magic Effects
Source of Effect Resists As Result of Dispel
Caster None Dispel automatic
Other caster/ Level/HD of
innate ability other caster Effect negated
Wand 6th level *
Staff 8th level *
Potion 12th level Potion destroyed
Other magic 12th, unless special *
Artifact DM discretion DM discretion
*
Effect negated; if cast directly on item, item becomes nonoperational for 1d4 rounds.
And given how the AD&D DMG is already full of "things players are not meant to know, ho ho ho", it's easy to look at something like this in a negative light (like the Assassin's knowledge of poisons).