The flame of justice is a more powerful (and in some minds, more twisted) version of the 1st-level fire truth spell. It is cast in much the same way, using a lit candle to determine truth or falsehood. However, the spell has two important changes.
First, this spell causes part of the target's body to burst into flame for each untruth spoken. The first untruth inflicts 1d4 points of damage, and each additional untruth inflicts 1d6. There is no saving throw against the casting of the spell, but for each untruth told, the recipient is allowed a saving throw vs. spell to halve the damage. Damage still increases with each untruth; the result is divided by two.
Second, the ideal of "truth" is subjective to the caster, not the target. If the caster believes something to be true, even if it is incorrect, the target suffers the effects of telling the (unappealing) truth. Telling the questioner what he wants to hear is an excellent method of surviving the spell. Ignorance or silence is not a defense if the caster believes the target is hiding something. Half-truths and outright lies can spare the target, provided that the caster believes in them. The DM must adjudicate in such situations, but only the evil and black-hearted rogue would choose to disbelieve everything said only for the purpose of inflicting damage.
The spell is limited to 10 questions or 10 rounds, whichever comes first. An attack on the caster breaks the spell, provided the attack inflicts damage. The flame of justice may aid a local ruler in trying someone accused of a serious crime, although in gentle, civilized lands, fire truth is preferred. Mages of the True Flame (wizards who follow only the province of flame and persecute wizards of all others) often use the flame of justice to extract confessions.
The material component of this spell is the same as that for fire truth-a candle made of a rare form of desert bee's wax. It costs 300 gp ready-made, and is available only through holy men (usually of the moralist faction). The wizard can make the candle himself in a week, after investing 100 gp in the raw materials, if these are available.
Notes: Common for the Mages of the True Flame; rare for others. Virtually unknown outside an Arabian setting.