Source: Pathfinder 5, Sins of the Saviors, pg(s). 84-85
The specter of a horrifying crone hovers several feet off the ground, her semitransparent body afire with otherworldly green flames. Her wild hair, tatters of ghostly clothing, and aura of eerie fire violently whip and waver, as if caught in some soundless hurricane.
A witchfire sometimes spawns upon the death of a hag, when one of these savage crones dies with some terrible plot unfinished or simply proves too maliciously tenacious to succumb to death's grasp. Appearing as spectral witches, with forms similar to but exaggerated from their former bodies, witchfires are typically between 5 and 7 feet tall, with some, particularly former annis hags, appearing larger and more powerful. The most distinct feature of the creatures are the flames that constantly whip and flicker about their forms as they float through their gnarled forest homes. These ghostly fires are widely believed to be the same "witchlight" or "witchfire" of rural legends, the mysterious luminescence thought to give light to will-o'-wisps.
Habitat & Society
Witchfires turn their surroundings into living nightmares. A witchfire typically remains in the same region she haunted in life, though in some cases the unfinished plot that ties her to the Material Plane might demand she travel far. While the horrors are usually found in dense forests and swamps, aquatic varieties raised from slain sea hags are not unknown. Areas frequented by witchfires for long periods grow foul and corrupt, as the witch's deathless malevolence seems to taint the very earth. Water goes stagnant, trees wither and become gnarled, animals flee or fall sickly and die, all in malign reaction to the spectral resident.
Although hags are likely to form quarrelsome coveys, witchfires are too proud and arrogant to seek out and join with other undead of their kind. Should a witchfire have been part of a covey in life, however, she is likely to seek out her sisters and attempt to subjugate them. If a witchfire deigns to suffer her sisters in death, the powers she brings to the covey are substantial.
Where, in life, most hags indulge in grotesque hungers, in death, they have no physical need to continue such depredations. This makes the fact that most hags continue to kill and mimic feeding all the more senseless and perverse an act. Witchfires delight in cursing creatures—man or beast—with witchflame, then tearing them apart. These acts serve only to delight their cruel senses of humor.
Although witchfires have no need to feed, the will-o'-wisps that often follow them do. The attraction of will-o'-wisps to witchfires seems to transcend the bounds of similar wickedness, as will-o'-wisps are capable of feeding off the emanations of a witchfire's aura. While this doesn't sustain them like true emotions of panic and horror, the witchflame seems to induce a state of malicious euphoria. This, coupled with the true terror and death that typically follows in a witchfire's wake, make will-o'-wisps eager to follow, even obey, these spectral hags.