It's particularly formidable in that it doesn't outright attack its target but instead feeds on the target's guilt, tormenting them to the point the person goes completely mad or they commit suicide.
According to scholars who wrote Behind the Great Veil, hyms are one of the most dangerous demons and cannot be exorcised traditionally. They inhabit several spheres, including the real world and Gaunter O'Dimm's dark plane.
- Some men have got good reason to fear their own shadows.
– Svargmitt, An Skellig druid
- Monsters most commonly claim innocents as their victims: tardy merchants, reckless children and travelers who wander into dark woodlands out of misplaced curiosity. None of the above need fear hyms, however. These wraiths only latch onto particularly despicable individuals who have committed some unspeakable crime. To all others, they remain completely invisible. When they do show themselves to the one they torment, they appear as a tall, shadow-clad, humanoid silhouette with long, sharp claws.
- Yet hyms do not sink these claws into their victims. Instead, they sap their strength directly, through inflicting suffering. Speaking in a voice only the victim hears, they drive him to commit acts of violence, aggression and self-harm. A hym will seize on a guilty person's worst fears and weave out of them hideous visions, slowing[sic] driving the poor soul into madness.
- Those tormented by a hym are incapable of restful sleep, for they are tormented by ever-more-frequent, incredibly-realistic nightmares. At times the victim will become extremely on edge, yelling pleas or threats at invisible phantoms or confessing his guilt out loud in the hope this will end his torment. This act does not, however, bring any relief, for the hym will not leave until it has addled its victim's wits completely or driven him to suicide.
Once a hym is exposed to possessing a victim, the witcher way of exorcism comes into effect. Moon Dust is unnecessary, but a silver sword coated with specter oil can help finish the fight quicker. Hyms do not move quickly, compared to other specters. Their ethereal claws have great reach, and they can sap the life out of their victims with a mere brush, which makes up for their slowness. Evade or roll past the claws and try to strike the hym before it can react. Be aware that after several strikes, the hym will teleport to another corner of its room.
The battle against Udalryk's hym took place in two phases, one in the main chamber of his old home, and one in the basement. During the first phase, the hym was being damaged whenever possible, using Igni sign to keep him visible while dealing good blows. As hyms often teleport but attack slowly, one should try and get damage in after every attack. When Udalryk began to succumb to the hym's madness, Axii sign had to be immediately used on him to force him to remain calm.
Igni and Yrden sign are both great help at keeping the pressure on the hym. Being lit on fire does not have an extraordinary effect on the hym, but it deals fair damage and helps keep it more visible, especially helpful in the cellar. Yrden slows down the already slow specter, making it easier to strike a blow. When the hym retreats to the cellar, pursue it quickly before it can regenerate. The cellar has candles you must light with Igni to help keep the hym corporeal. Continue fighting defensively, evading its claws and striking as openings present themselves until the hym succumbs.
- Killing the Hym via the witcher's way will provide loot after its death, trickery will not.
- When looking for the sword Brokvar in the basement of the old home, the hym can be spotted on one of the walls for a brief moment when the sword is looted.