by SyntheticGod8 » Mon Sep 23, 2013 6:13 pm
I would agree with Dyson that, while the auras of magic items held by an Invisible mage might not be visible under Detect Magic, the person is under the effect of a spell. However, this doesn't mean that the Invisible mage has been conclusively detected. All that would be seen is an indistinct aura (of the Illusion school if you wanted to be specific) in a 5' diameter area (height is up to you). Knowing what's in there is impossible without more magic or using other senses (like touch). Hitting whatever's there with a melee or missile weapon would entail at least a -4 penalty to-hit and targeting it with a spell like Ray of Enfeeblement or Hold Person would be impossible, since there is no visible target.
Using Detect Invisible would make the target appear either as normal or as translucent (DM's choice). Either way, there's no penalty to fight them or target them and the mage knows that he's spotted an Invisible creature. The Invisible creature might still be Hiding in Shadows, of course.
I've had a similar problem with Darkvision. One my players argues that, since Darkvision works on the infrared spectrum, that footprints and invisible creatures would be visible in total darkness. I personally don't think footprints would stay hot enough or be detectable for more than a few moments before they're too muddled to be sure they're footprints. As for Invisibility, I allowed him to detect a warm 5' area with no visible source. Point is, Darkvision is meant to simply be an advantage that lets a creature with it to function in complete darkness, albeit in a crude, rudimentary way (he can make out objects, obstacles, creatures, but no detail). Similarly, Detect Magic is meant to detect the presence of magical auras, to give a clue that things aren't what they appear, not to negate all forms of illusion by allowing form or pin-point accuracy.