Detect magic

Detect magic was a divination spell   that was sometimes categorized as a universal spell. It allowed the caster to become aware of magical emanations in the direction the caster was facing, within range of the spell. After the Spellplague, it became a trained skill for those with affinity for magic.

Effects
Over the years, this spell has evolved, growing in capability while becoming easier to learn. Early illusionists didn't learn this spell until they reached second level while divine and other arcane casters could learn it at first level. Eventually this spell became a cantrip for wizards and an orison for priests. After the Art recovered from the Spellplague, a spellcaster could be trained to identify rituals, magical effects, and even sense the presence of magic through most any barrier.

At first, each practitioner of magic had their own version of detect magic. Magic-users including illusionists could sense magic in a 10 ft (3 m) wide corridor 60 ft (18.3 m) long and for a duration based on their experience level. Clerics and druids could only "see" magical auras out to 30 ft (9.1 m) and 40 ft (12.2 m) respectively for a duration of 10 or 12 minutes respectively. The caster could turn in an arc to sweep out an area, making a full circle in six minutes. These versions of the spell could penetrate anything less than 1 ft (30 cm) of stone, 1 in (2.5 cm) of solid metal, a thin sheet of lead, or 3 ft (0.9 m) of wood or dirt. No information other than the presence or absence of magic was acquired.

Later, wizards and priests were able to determine the intensity of magical auras, classifying them as dim, faint, moderate, strong, and overwhelming. In addition, wizards had a chance to identify the school of magic to which an aura belonged. Priests were likewise able to identify the sphere of magic. The more experienced the caster, the better were the chances to correctly identify each aura. Once again, the divine spellcasters had a fixed duration of 10 minutes but could "see" out to 90 ft (27.4 m). Arcane spellcasters could only detect out to 60 ft (18.3 m) but the duration was based on their level and eventually exceeded the divine version's 10 minutes for more experienced wizards.

The orison/cantrip version of detect magic was effective in a cone-shaped area out to 60 ft (18.3 m) and revealed information depending on how long the caster studied a particular area or subject, but even so it was much faster than earlier versions. The spell supplied indications in three stages:

First, the caster could feel the presence or absence of magical auras. As the caster concentrated further, the number of different magical auras and the strength of the strongest was evident. And finally, knowledge of the strength and location of each aura was revealed, with a chance to determine the school of magic if the aura was in line-of-sight. If an aura could be placed in more than one category, detect magic indicated the stronger of the two. Likewise, strong emanations could mask or distort weaker ones.

Magical effects left a residual aura that faded with time. How long this residual aura could be detected depended on its original strength. The caster was able to get a dim reading on a faint effects for only a few seconds after the effect ended. Moderate to strong effects left a lingering aura for a few minutes to an hour. Overwhelming magical effects were still detectable for a few days afterward.

The orison/cantrip version was also blocked by the same materials as previous versions. After the Spellplague, arcane practitioners could be trained to analyze and identify magic rituals and effects as long as they had line of sight to the area of interest. In addition, they could sense the presence of magic regardless of barriers.

The post Second Sundering version of the spell lasted 10 minutes and only reached 30 feet (9 meters). In this zone the caster could feel the magic's presence and determine the spells school see it as a vague aura. the spell could not penetrate 3 feet of wood or dirt, 1 foot of stone or 1 inch of steel or a slim sheet of lead.

Components
All versions of detect magic required verbal and somatic components. The divine versions also required the use of the caster's holy symbol or divine focus.

Inscription
According to the Book of the Silver Talon, the ingredients for the ink used to inscribe detect magic into spellbooks were: one ounce of giant squid sepia, a small, powdered sapphire, one drop of spring water, one drop of blood from the writer, a single object that radiated dweomer and enough oak, ash and thorn branches to start a fire.

The sepia was heated over a fire made from the various woods to which the powdered sapphire, water and blood were then added. This had to be stirred with the mixthorn branch which was then added. Once the fire burnt out it would sit until cooled and then stored in a flask or other vessel.

History
This very basic spell predated the period of spell invention of the Netherese and was taught to the humans by the Earlanni elves in the early days of Netheril. The arcanist Trebbe developed a similarly named mentalism, Trebbe's scry magic, in 1589 NY (−2270 DR), but its effect was lost, so the relation between the two spells remained unclear.

Detect magic was a common spell in the 1360s DR in both Faerûn and Zakhara. It was one of the spells available from the Balance of Belaros, a holy relic of Tyr.