Candle's insight

Candle’s insight is cast on its target as the component
candle is lit. The candle burns for up to 10 minutes
unless it’s extinguished normally or by the spell’s effect.
While the candle burns, the caster can question the
spell’s target, and the candle reveals whether the target
speaks truthfully. An intentionally misleading or partial
answer causes the flame to flicker and dim. An outright
lie causes the flame to flare and then go out, ending the
spell. The candle judges honesty, not absolute truth; the
flame burns steadily through even an outrageously false
statement, as long as the target believes it’s true.
Candle’s insight is used across society: by merchants
while negotiating deals, by inquisitors investigating
heresy, and by monarchs as they interview foreign
diplomats. In some societies, casting candle’s insight
without the consent of the spell’s target is considered a
serious breach of hospitality.