Sluagh

Each member of the sluagh, called 'the host,' resembles a sprite turned to shadow, with a dark, murky body and shimmering, gauzy wings. Packs of them fly by night, and at twilight from a distance the host looks like a churning thunderhead, sometimes lit from within by shifting blues, greens and reds. Up close the 'cloud' proves to be hundreds of bird-sized spirits, each carrying a tiny bow and a little sword at its waist, with zombies borne along magically in the middle of the swarm.

The host shoots tiny poisoned arrows out to 75 yards. A creature struck saves vs. poison or dies within 2-5 rounds, barring slow poison or neutralize poison. Only one save is ever required: a character who survives becomes permanently immune to sluagh poison. In melee they use tiny swords that hit as hard as daggers. Any member may cast animate dead or fly, one spell per round, without limit. Anyone they kill is raised as a zombie and carried away when they leave, and a host is usually escorted by 3-24 zombies already under its command.

Sluagh never check morale normally, though the DM may have them fly off whenever they have just claimed a new zombie. They seethe with barely restrained fury and fight each other whenever no living prey is handy; legends describe great sky battles between rival divisions. Clever characters can often goad large groups into fighting among themselves and forgetting the party.

Sleep, charm, hold and cold spells have no effect, nor do poison and paralysis. Each vial of holy water deals 2-8 damage, and raise dead or resurrection destroys one outright. Clerics turn them as ghouls and in the same round get a separate attempt against their zombie escort.

The host consists of the ghosts of warlike elves who betrayed their own people and died in battle. They travel in large war bands, only in the wilderness and never in dungeons, favoring bleak highlands and moors. They shun daylight and never appear before dark. Bigger hosts have undead officers: a wraith lieutenant for every 20 sluagh, a vampire captain for every 40, and a lich commander once the host reaches 80 or more. Use such leaders only with high-level parties that have some hope of turning them.

The idea comes from Highland Gaelic legend, where the sluagh (said 'SLOO-ah') are the restless, unforgiven dead. In the old tales they swirl through the sky like flocks of starlings, return to the places of their sins, shelter on foul nights under dock and ragwort stalks, and wage aerial wars that leave crimson blood on the rocks after a frosty, moonlit night. They kill livestock and pets with poison darts and can force men to follow them and do murder at their command, treating these servants without mercy.