School divination; Level bard 0, cleric 0, druid 0, sorcerer/wizard 0
Casting Time 1 standard action
Component: V, S
Range 60 ft.
Area cone-shaped emanation
Duration concentration, up to 1 min./level (D)
Saving Throw none; Spell Resistance no
You detect magical auras. The amount of information revealed depends on how long you study a particular area or subject.
1st Round: Presence or absence of magical auras.
2nd Round: Number of different magical auras and the power of the most potent aura.
3rd Round: The strength and location of each aura. If the items or creatures bearing the auras are in line of sight, you can make Knowledge (arcana) skill checks to determine the school of magic involved in each. (Make one check per aura: DC 15 + spell level, or 15 + 1/2 caster level for a nonspell effect.) If the aura eminates from a magic item, you can attempt to identify its properties (see Spellcraft).
Magical areas, multiple types of magic, or strong local magical emanations may distort or conceal weaker auras.
Aura Strength: An aura's power depends on a spell's functioning spell level or an item's caster level; see the accompanying table. If an aura falls into more than one category, detect magic indicates the stronger of the two.
Lingering Aura: A magical aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a magic item). If detect magic is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power...
Detect magic specifically does detect active spells, yes. However, if you're asking what it detects if you happen to cast a spell when someone else has detect magic active, then (assuming they're facing their cone of effect in the right direction in the first pace) at the moment the spell is cast they only detect that there is a magic aura in the area they're scanning (i.e. the one round's worth of study result). So, if there was already at least one aura in the area, they won't detect anything 'extra' in that instant.
** spoiler omitted **
Detect magic specifically does detect active spells, yes. However, if you're asking what it detects if you happen to cast a spell when someone else has detect magic active, then (assuming they're facing their cone of effect in the right direction in the first pace) at the moment the spell is cast they only detect that there is a magic aura in...
ok..if in the area there is a +1 magic item detect magic don't detect if a player cast a spell? and d.m. can't detect who cast that spell?
Well, the DM can detect whatever he wants... but if he's playing his NPCs by the rules then detect magic alone wouldn't detect anything extra in the instant the spell was cast, no. On round two (once the spell is cast) the NPC (who is still concentrating on his detect magic) will sense that there is an extra aura, and its strength if it happens to be the most powerful aura in his detection area now. On round three he can sense the strength and location of the spell's aura, and - if it's also in line of sight - can make some rolls to try to identify it exactly. Even low-level spells have auras which 'linger' a bit, so it's possible he could do this even if the spell itself was 'instant'. On the other hand, nothing in detect magic itself allows him to know who cast the spell (although if he happens to ID it as a spell he knows is personal range he can probably guess who cast it).
To spot people casting spells will usually be down to straight Spellcraft checks anyway - no magic required.
...To spot people casting spells will usually be down to straight Spellcraft checks anyway - no magic required.
I wouldn't even go that far.
You see some guy waving his hands around, gesticulating madly, intoning words in no language that you've ever heard of before while throwing powder in the air. Odds are, he's a caster who is currently casting a spell.
If 10 of them are doing it, spellcraft will tell you which is faking it, and which ones are the real casters, but casting generally isn't a subtle thing.
I always was of the opinion that spells aren't "wiggle your nose and watch someone else's face explode" like Bewitched on a bad day. They are complicated (short) rituals. Whether it's a cleric performing hymnal chant in angelic, or a sorc screaming reality into submission, it's something that is fairly easily noticed. Concentration checks represent of you can keep your place in the spell and no replace "And be most wrothful in thine gaze" with "DAMMIT! I NEED THOSE FINGERS!"
Once you drop Still, Silent and Eschew onto the spell... then... yeah... can be subtle.... but a fireball still streaks from YOUR square to the target.