The character can detect the aura that surrounds undead. The amount of information revealed depends on how long the character studies a particular area or subject:
1st Round: Presence or absence of undead auras.
2nd Round: Number of undead auras in the area and the strength of the strongest undead aura present. If the character is of good alignment, the strongest undead aura’s strength is "overwhelming" (see below), and the strength is at least twice the character's character level, the character is stunned for 1 round and the spell ends. While the character is stunned, the character can’t act, the character loses any Dexterity bonus to AC, and attackers gain +2 bonuses to attack the character.
3rd Round: The strength and location of each aura. If an aura is outside the character's line of sight, then the character discerns its direction but not its exact location.
Aura Strength: The strength of the undead aura is determined by the HD of the undead creature.
Strength HD Dim Lingering aura Faint 1 or less Moderate 2–4 Strong 5–10 Overwhelming 11+
Length Aura Lingers: How long the aura lingers depends on its original strength:
Aura Strength Duration ------------- --------
Faint 1d6 minutes Moderate 1d6 X 10 minutes Strong 1d6 hours Overwhelming 1d6 days
Note: Each round, the character can turn to detect things in a new area. The spell can penetrate barriers, but 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt blocks it.