The Slaugh, when I first introduced it into my daughter's game, was looked upon with fear, and even now months later the mere mention of a "flock" of these undead creatures sends the tough barbarian running for the nearest inn or Temple of Eira.
Remember, everything presented on the Genius Loci blog is an alpha version of a creature/race/class/item/etc. and may not work completely insync with OSR rulesets.
Armor Class: 4 
Hit Dice: 3+3
Attacks: Claw or bite (1d6)
Special: See below, Immune to magical effects
Slaugh are the restless souls of cursed men who cannot find rest and are damned to forever wonder the earth. Twisted by their curse, Slaugh will attempt to damn others so as to share in their pain and will often appear near the dying to take their souls and twist them (30% chance)
Slaugh roam the world in groups of at least three. Being cursed and rejected, the Slaugh cannot touch earth as it causes them great pain (1d4 damage per round) and thus float between 12 and 18 inches above any surface.
Specials: Curse: Anyone killed by a Slaugh is cursed to rise as a Slaugh in 1d6 days of their death and seek the flock of the Slaugh that killed him.
A Slaugh cannot be killed unless their body is in contact with the earth long enough for the Slaugh to reach negative HP equal to his full HP. If this does not occur the Slaugh will rise in 1d4 hours of his "death".