© Nana Yaw Ofori (firstname.lastname@example.org) 1996What does Detect Magic do? With a cost of 2 fatigue points, and a casting time of 5 seconds, it determines whether any one object is magical, and a second casting determines whether the spell is temporary or permanent. It's also a springboard towards Mage Sight, Mage Sense, Identify Spell, and Aura.
In the standard Normal Mana world, only mages can cast this spell. Problem is, Mages, as written, already have an innate version of the spell. On an IQ+Magery roll, mages detect magic items. If you're getting the standard crop of IQ 14, Magery 3 mages, it means magic items are detected on a 17 or less. That situation makes Detect Magic of rather limited utility, in my opinion.
So here are a couple fixes:
Could use a little explanation on what the mages' innate magic-detection ability detects. Offhand, I'd say it detects permanent Enchantments on non-living creatures. So, for instance, it would tell said mage whether a tomahawk had the 'Accuracy' spell cast on it, but would give you no clue whether a fog was created by the Fog spell or was natural (Though the fact that said fog is circular, has well-defined boundaries, and extends to a uniform height of 12 feet would probably tip you off). It would not sense permanent magic spells on living targets. If somebody ensorceled themselves with the Flight spell, the innate ability would not sense it.
Also, if it's not automatically considered to do so, I'd probably adjust the description of Detect Magic so that it specifically says that the spell is useful not only for objects, but for living beings as well. [I would rather leave that to the Aura spell. -- Incanus]
Here's one of the fixes I've decided to add. Instead of working off an IQ+Magery roll, the Innate ability is based off a Magery roll, the type that is already used for detecting changes in the Mana Level. That is, Magery 1 has a success roll of 8, Magery 2 on an 11, and Magery 3 on a 13. Instead of having a 98% chance of detecting that enchanted tomahawk, that IQ 14, Magery 3 mage only has an 84% chance of detecting the enchantment. Not as much of a sure thing anymore. Detect Magic learned by said mage will bring his magic-detection ability up somewhat.
Another change. Instead of operating once when the mage sees the object, and again when the mage touches the object, the Magery roll is only given when the mage touches the object. Gives another advantage to learning Detect Magic: it's a ranged ability. Detect Magic will tell you the sword has a spell on it before you pick it up and the Hex and Strike Blind enchantments are activated. (Of course, you'll probably pick it up anyway, and bring both effects down upon yourself, regardless.) A Mage with the Second Sight advantage (GURPS Compendium I, page 43) may use the Innate Ability at up to a 1-yard range.