Etarlam is a son of Mannan and has lived almost since the beginning of time. He is much older than the Wild Hunt, and much more powerful. In the old days he hunted giants and monsters with his siblings, but chose to serve the Unseelie King as one of his assassins.
In 2012 Etarlam and his siblings were sent after the Blackthorn family to retrieve the Black Volume of the Dead for the Unseelie King. Etarlam went after Kit Herondale and the twins Ty and Livvy Blackthorn in London, along with Karn and Eochaid.
In London Etarlam fought Kit and the twins alongside his siblings until the fight was interrupted by Gwyn ap Nudd and Diana Wrayburn. He was shocked when Eochaid proclaimed that their brother Fal was dead, but immediately felt his brother's death himself and fell to his knees before leaving with his brothers to join their siblings in Cornwall.
Etarlam later joined his surviving siblings in attacking the London Institute. He fought against Cristina Rosales and was about to kill her when Annabel Blackthorn appeared and threatened to reveal the Unseelie King's name. Etarlam tried to attack her but was thrown into a nearby wall. He then retreated with his family.
Like all the Riders of Mannan, Etarlam is arrogant and confident in his abilities.
Etarlam is tall with long bronze hair and a bronze half mask on his face. He wears a bronze cloak and armor etched with designs of the sea and waves.
- Longevity: As a Rider of Mannan, Etarlam is very old and has been alive for thousands of years.
- Enhanced Strength/Speed: Etarlam is able to move incredibly fast and deal heavy blows.
- Invulnerability: Etarlam is immune to most magic, such as seraph blades, and cannot be killed by conventional means.
- Lord of Shadows (first appearance)
In Celtic mythology Etarlam was a druid of the Tuatha Dé Danann, a race of supernatural beings.