You psionically reach across the planes to form a temporary bond with the Negative Energy Plane. Drawing deeply on your link, you ignite a pillar of black flame that rises from the ground into the sky. Each creature caught in the area of effect gains 1d4 negative levels.
There is no saving throw to avoid gaining the negative levels, but 24 hours after gaining them, an affected creature must make a Fortitude saving throw (DC equal to the stygian conflagration's save DC) for each negative level. If the save fails, the nagtive level still goes away, but one of the subject's character levels is permanently drained.
An undead creature in the area gains 1d4×5 temporary hit points that last for up to 1 hour.
For every 2 additional power points you spend, the power bestows one additional negative level, and affected undead gains 5 additional temporary hit points.