Fairy Facts: Slua Sidhe

 For this installment of fairy facts we're going to take a look at the Slua Sidhe, beings found in folklore as well as incorporated into modern Role Playing Games (RPGs). 

Åsgårdsreien by Peter Nicolai Arbo

Name: Slua Sidhe (Irish) or Sluagh Sìthe (Scottish)
In Irish the name translates to the Fairy Host or Army. In Gaidhlig the terms means Fairy People, Fairy Host
In Scotland the term may be shortened to Sluagh, while Sluagh na Sìthe is a poetic term for the fairies

Please note the term slua or sluagh is a collective noun which describes a group of beings, a host or crowd, not an individual being. 

Description: a group of malicious or dangerous beings who travel primarily through the air using magic. May or may not be on horses or accompanied by hounds.

Found in Irish and Scottish folklore, and in Irish mythology

Folklore: in Irish folklore the Slua Sidhe (modern Irish Slua Sí) are malevolent fairies who travel in whirlwinds or gusts of wind and who are prone to both kidnapping humans and causing injuries to those they pass. They might swoop down and abduct any solitary human who takes their fancy, sometimes keeping them and sometimes dropping them very far from home. Those they injure may be blinded, lamed, or driven mad, if not outright killed. According to Katherine Briggs they are most active at night. In older Irish material and myth the Slua Sidhe are simply any army of the Aes Sidhe.

In Scottish folklore the Sluagh may be understood as fairies but are also described as being the unforgiven human dead, who kill animals and restlessly wander the skies. It is believed that they lived wicked lives as humans and must therefore atone for their sins by wandering the earth without rest. They may employ elfshot, invisible arrows, against their victims, and by some accounts serve or are driven by another spirit; Alexander Carmichael in his Carmina Gadelica doesn't name or describe these beings, only referring to them as 'spirit-masters'.

Irish folklore has a different term, slua na marbh, for the host of the dead, however Gaidhlig doesn't differentiate the two in the same way. 

Where It Gets Muddy: The sluagh appear in Changeling: The Dreaming, an RPG put out by White Wolf. However the sluagh of the RPG are vastly different from those of folklore, not only because the term is (mis)used as an individual noun but also because they are said to live underground; the other name used for them us 'Underfolk'. They are primarily associated with causing fear. The RPG sluagh are bound not to cause any real harm and work to frighten children into good behaviour. 
In short the RPG sluagh are entirely different beings than those of folklore, however many people who are only familiar with the gaming concepts are unaware of that. 

What They Aren't: As noted above, Slua is not an individual term. A person cannot be 'a slua', as that literally means a host or crowd. An individual would be a member of the slua.
The Slua are not psychopomps, nor are they associated with stealing newly dead souls (only still living humans). 
The Sluagh do not have wings. They fly via magical means rather than a physical appendage.