Cairn is the Fae male who assumed Rowan Whitethorn's place in Maeve's cadre after Rowan left Maeve's service.
Cairn has brown hair and blue eyes. Elide notes he might have been handsome if not for the obvious sadistic cruelty radiating from him.
Before the Series
Rowan mentions that Cairn was once part of his army while he was under Maeve's command and that no matter what he did (lock him up, flog him, discipline him or try show compassion towards him), Rowan couldn't break Cairn sadistic personality. He therefore kicked Cairn kicked him out of his own army and dumped him onto Lorcan's lap, where he lasted only a month before he was transferred to an isolated legion. Rumour says that he did unspeakable things to both the soliders and civilians he came into contact with.
Empire of Storms
Fenrys and Gavriel reveal to Rowan that Maeve has replaced him with Cairn. Rowan expresses horror upon receiving this information, recalling his failed attempts at ridding the warrior of his sadism. When Lorcan also failed the same objective, Cairn was sent to an isolated legion.
Cairn appears in person when Maeve confronts Aelin Ashryver Galathynius on the beach along the Gulf of Oro. Under Maeve's command, Cairn brutally whips Aelin and even smirks at the tattoo on her back. Before departing with Maeve, he deliberately leaves Aelin's shirt behind in the pool of blood as a message to Rowan.