Publication:Dread Codex/Monsters/Phantasm

''This entity appears as a translucent humanoid with faintly discernible facial features twisted and corrupted by evil. Its arms are long and thin and trail off in wisps of immaterial matter.''

Phantasms are malevolent and sinister spirits that delight in the destruction of good-aligned creatures. While many undead creatures are the undead form of once living creatures, phantasms have no real material connection to living creatures; they are spirits born of pure evil. They are most often found haunting ruined temples or churches dedicated to evil gods, or dungeons constructed by evil creatures; any place where the stench of evil permeates the very air.

Combat
A phantasm begins battle by attempting to possess a foe, and if successful, it then controls the host like a puppet. In addition, while possessing a foe, it is constantly sapping its life energy. When the host is destroyed, the phantasm leaves the body and attempts to repeat the process on any opponents still in the area.

 (Su): The incorporeal touch of a phantasm deals one negative level. The Fortitude save to remove a negative level has a DC of 22. The save DC is Charisma-based. For each such negative level bestowed, the phantasm gains 5 temporary hit points.

 (Su): Once per round, a phantasm can merge its body with a creature on the Material Plane. This ability is similar to a magic jar spell (caster level 9th), except that it does not require a receptacle. To use this ability, the phantasm must try to move into the target's space; moving into the target's space to use this ability does not provoke an attack of opportunity. The target can resist the attack with a successful DC 17 Will save. A creature that successfully saves is immune to that same phantasm's possession for one day, and the phantasm cannot enter the target's space. If the save fails, the phantasm vanishes into the target's body.

A phantasm automatically deals one negative level (from its energy drain ability) each round to its host. The host can eject the phantasm with a successful DC 17 Will save. This save can be attempted once per round. If successful, the phantasm is forced from the host's body and it cannot attempt to possess the same host for 1 minute. If turned or subjected to a dismissal spell while possessing a host, the phantasm is ejected. The save DCs are Charisma-based.

 (Su): A phantasm has a continuous aura of desecration that affects a 10-foot radius. This aura can be dispelled, but the phantasm can restart it again as a free action on its next turn. All turn attempts made within the aura suffer a -3 profane penalty; all undead within or entering the aura gain a +1 profane bonus to attack rolls, damage rolls, and saves (these bonuses are already included in the phantasm's stat block). This ability otherwise functions as a desecrate spell.

 (Su): Both wild and domesticated animals can sense the unnatural presence of a phantasm at a distance of 30 feet. They will not willingly approach nearer than that and panic if forced to do so; they remain panicked as long as they are within that range.

Treasure
None — As incorporeal creatures without a humanoid origin, the phantasm carries no treasure; indeed, it deems such items as worthless.

In Your Campaign
Left to their own devices, phantasms keep to the areas described above (old evil temples, etc.). But when commanded by highlevel clerics or necromancers, phantasms often serve as standard bearers of a sort in large undead battalions. Within the masses, phantasms bolster the undead around them until they are able to surprise enemies who break through the lines.

As a being formed from pure evil, you should have the phantasm perform the most heinous acts imaginable while possessing a humanoid body (at least as far as your group's decorum allows). Specifics are perhaps best left to the imagination. Once a phantasm does leave a host body then that body should carry some sort of scarring. Without altering game balance, you could age the body's appearance one year for every negative level inflicted while possessed. Depending on the host's race, gray hair and wrinkles might now be evident where there was recently youthful color and tone.