When the Detect Magic spell is cast, the wizard detects magical radiations in a path
10 feet wide and up to 60 feet long, in the direction he is facing. The intensity of the
magic can be determined (dim, faint, moderate, strong, overwhelming), and the wizard has
a 10% chance per level to recognize if a certain type of magic (alteration, conjuration,
etc) is present. The caster can turn, scanning a 60 degree arc per round. A stone wall
of one foot or more thickness, solid metal of one inch thickness, or a yard or more of
solid wood blocks the spell. Magical areas, multiple types of magic, or strong local
magical emanations may confuse or conceal weaker radiations.
Certain magical radiations are deliberately designed to be more difficult to detect,
which limits the usefulness of Detect Magic. These types of "concealed wizardry"
cannot be detected by a casual sweep of Detect Magic. However, by casting the spell
upon a specific item, "concealed wizardry" can be overcome. Whether or not the
chosen item reveals to be magical, this application of the spell ends after a single
use.
Note that this spell does not reveal the presence of good or evil, or reveal alignment.
Other-planar creatures are not necessarily magical.
As all my gaming friends know, I'm a fan of the gnomish race and their intricate
illusions. Their penchant for illusions must have a source, a cause - I would guess that
illusionary magic was fostered as a defensive measure against the larger and stronger
races of the world. Then I noted an interesting section of the Complete Book of Gnomes
and Halflings, a section that reads something like this:
"On the practical side, illusionary magic is not usually employed to screen the
location or nature of a gnomish community. Though such arcane devices might prove
effective at concealing them from mundane detection, the emanation of magical power
actually serves as a beacon to those who use such spells as Detect Magic."
So, here we have a very interesting and story-provoking racial trait, yet the trait
is extremely restrained (if not rendered worthless) by a mere 1st level spell. Why did
gnomes even bother with illusionary magic, given that they cannot use it effectively for
community defense?
This avenue of thought led to other, similar notions - the workings of Detect
Magic has detrimental effects upon the campaign world as a whole. It's just too easy
to be able to pinpoint the location of magical items and effects, especially in situations
where there is a deliberate attempt or need to conceal the magic. How to fix? Well, the
beginning of the solution came from the Al-Qadim setting, and it's concept of "Concealed
Wizardry".
In the Al-Qadim campaign setting, magical items can be constructed as to not register to
such divinations as Detect Magic. This started me thinking - if magical items can
be designed as to be transparent to Detect Magic, then couldn't the same be done
with spells? This precedent led to the above revised spell, and the allowance for the
possibility of concealed wizardry. In my campaign, certain spells that have a need for
inherent concealment are considered to have been designed as concealed wizardry spells,
most notably a majority of the Illusion/Phantasm spells. No more using Detect Magic
as a cheap alternative to True Seeing. No more questions on what is revealed when
a Detect Magic is cast with an Invisible creature nearby.