This one appears in various forms in German and Scandinavian myth. Its another one that'll fit in nicely as a whole adventure for low level characters, trying to hunt down whatevet it is travelling from village to village causing carnage.
Erlkling
by Cab Davidson
Stat Erlking AC: 6 HD: 3* Movement Rate: 120’(40’) Attacks: 1 touch or 1 weapon Damage: Delayed Energy Drain or by weapon Number Appearing: 1d4 (1d4) Save As: F3 Morale: 9 Treasure Type: (C) Intelligence: 9 Alignment: Chaotic XP Value: 50 Erkling are among the most cunning of the undead. They look like elves, with the visage of wise, elderly, sage like sylvan elves, but their prey is typically human.
Appearing as wizened old elves they enter villages as soothsayers, pretending to be able to foresee the future. Specifically they claim to be able, by touch, to be able to predict when someone will die, and they practice in developing credible stories. Any resident agreeing to this foretelling must allow the erlking to touch them, at which point their fate is sealed. 2d12 hours later, they are subject to an energy drain, and if they are normal humans or first level characters that energy drain is of course fatal. By this time, the erkling will be long gone, travelling on to another village.
An erkling can drain up to 4 creatures in one night, to a maximum 13 over the course of a week. Frequently the first that members of a community are aware that something is amiss is when people start dying, and usually from the pattern of who died they can determine what the cause was. Hence erklings must continually travel, seeking new victims in new villages and towns. They understand the value of treasure, and frequently carry coin and jewels.
The means by which erklings reproduce is unknow. The fallen do not reanimate as erklings, they are found lying in their villages dead, staring upward at the sky in deathly terror.
Erklings, being undead, can be turned as if wights.