Detect evil

Detect evil was a divination spell that provided information about objects or creatures with an evil aura. Some versions of this spell were reversible, becoming detect good, and operated in the same manner but for good auras instead.

Effects
There have been a few different versions of this spell over the years, but they all worked in about the same way: the caster concentrated in a particular direction and learned about any creatures or objects that radiated evil in the direction viewed.

The newer, cleric-only version of this spell had a cone-shaped area of effect and a range of 60 ft (18.3 m). Auras could be detected even with some interposing structures or surfaces, within limits. Anything less than 3 ft (91 cm) of dirt or wood, 1 ft (30 cm) of stone, or 1 in (2.5 cm) of common metal could be penetrated, but a thin sheet of lead was proof against this divination. Upon first casting this spell and concentrating for a few seconds, the presence or absence of evil could be known. After a few seconds more, the most powerful aura was easily detected and a count of all detectable auras was possible. Upon further examination, the caster would know the power and location of each detectable aura, or at least their direction if out of the line of sight.

After gleaning all that could be perceived in one direction, the caster could turn and look in another direction, subject to the duration of the spell.

Auras were described by their strength, being dim, faint, moderate, strong, or overwhelming. Dim auras were those left behind after the death of an evil creature or the expiration of an evil spell, or perhaps after an active evil presence departed the area, and they lasted for a few seconds to a few days depending on the strength of the original aura. Active auras ranged from faint to overwhelming. Casters of good alignment could be stunned for a few seconds by detecting a sufficiently overwhelming evil aura. If this happened, the spell was canceled.

Examples of things that gave off an evil aura: evil creatures such as rakshasa, undead, clerics of evil deities, evil outsiders, evil magic items, evilly cursed objects, unholy water. Things that did not give off an evil aura: traps, poisons, animals.

The older versions of detect evil had a corridor-shaped area of effect, with the divine version having a range of 120 yd (110 m) and the arcane version half that. Priests also had a slight chance of perceiving the disposition (malignant, gloating, or expectant, for example) of an evil aura and where it stood on the lawful/neutral/chaotic spectrum.

Components
All divine versions of this spell required verbal and somatic components plus the use of the priest's holy symbol or divine focus. The arcane version did not need any materials. All versions required the caster to stand quietly still and concentrate after the spell was cast.