Source Pathfinder #27
Aura moderate necromancy; CL 10th
Grave candles are magical candles that draw forth spirits from the mortal remains of long-dead creatures, allowing the living to speak to them for a short period of time while the candle’s wick burns.
In order to function, a grave candle must be placed amid the physical remains of the body to be spoken to. These remains can be partial, or even just a handful of ash or grave dust, but a totally destroyed body (as results from destruction or disintegrate) doesn’t leave enough material for a grave candle to function. When it’s lit, the smoke rising from the candle grows thick, and a ghostly shape similar to the creature’s appearance in life manifests in the smoke.
At this point, the manifested spirit (which is as much an echo of the creature as it is the actual departed soul) can speak — a grave candle does not impart any additional understanding of languages. In other respects, the conversation with the dead spirit adheres to the rules for speak with dead, save that the dead spirit receives a –4 penalty on its saving throw to resist the spell. Furthermore, a dead body can only be successfully subjected to a grave candle once — the burning of the candle “burns out” the latent necromantic and spiritual energy left behind by the soul’s parting from the world (this does not harm the actual soul of the dead spirit).