Bastellus (5e Creature)
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Medium undead, neutral evil
Damage Vulnerabilities radiant
Incorporeal Movement. The bastellus can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.
Innate Spellcasting. The bastellus's innate spellcasting ability is Wisdom. The bastellus can innately cast the following spells, requiring no components:
Incorporeal Touch. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 16 (4d6 + 2) psychic damage.
Dream Invasion (3/Day). When the bastellus touches a sleeping humanoid creature it experiences horrifying nightmares, which provide the dream stalker sustenance and pleasure. A protection from evil and good spell cast on the target prevents this contact, as does a magic circle. If the nightmares last for at least 1 hour, the target gains no benefit from its rest, and its hit point maximum is reduced by 13 (3d8). If this effect reduces the target's hit point maximum to 0, the target dies. The reduction to the target's hit point maximum lasts until removed by the greater restoration spell or similar magic. The spirit of a humanoid creature slain by this effect rises 24 hours later as a bastellus, unless the humanoid is restored to life.
In many cultures, this predatory undead is known simply as a nightmare. Others lands call it a dream stalker. Regardless, this undead creature comes in the night to feed upon the psychic energies of dreaming sleepers. Once the bastellus has fed upon a person's dreams, it becomes obsessed with that individual and will return to taste their essences nightly until the victim dies. Once its prey has died, the bastellus moves on in search of another energetic mind upon which to feast.
Undead Nature. A bastellus doesn't require air, food, drink, or sleep. However, it does require the life energy of sleeping people to sustain its undeath.