Fenrys is a member of Maeve's cadre. He has a twin brother named Connall, who is also part of the cadre.
Fenrys took the blood oath to Maeve after learning that Connall took the oath to step out of his shadow. He is serving Maeve in bed to keep his twin from her clutches. It is no secret that Fenrys despises Maeve and the blood oath.
Fenrys is described as having dark onyx eyes, bronze skin and golden hair, alongside other standard Fae features such as slightly pointed ears and sharpened canines. He is also described as incredibly beautiful on more than one occasion by various different characters. He can shift into a white wolf.
He is sardonic and witty. He is fond of saying things that get on people's nerves.
Fenrys is seen to be incredibly loyal to Aelin, although he has not really known her for very long. He admits that the blood oath he has with Maeve is not what an oath truly should be, and tells Aelin that Fae males are all looking for someone worthy to protect, serve and cherish, and that what Maeve offers is only a mockery of that.
Like most Fae, Fenrys has an animal form. His animal form is that of a massive white wolf. Fenrys also has the power of transportation, unlike other Fae who mostly have elemental gifts; he describes his rare ability as something that allows him to "slip between folds in the world". He states that this ability only allows him to travel short distances and he can only use this ability a few times before he is drained. As a Fae, he also has all the standard powers that they have, including swift healing, increased strength and speed, and enhanced senses.
Fenrys took the blood oath to Maeve after learning that his twin brother, Connall had taken the blood oath in order to step out of his shadow. Fenrys is serving Maeve in bed to keep his twin from her clutches. It is no secret that Fenrys despises Maeve and the blood oath.
Fenrys has only a small part in Heir of Fire - he answers Rowan's call for aide and helps in the battle at Mistward, and is present along with the rest of the cadre when Aelin comes to Doranelle to show Maeve what she has learned and exchange information.
When Maeve confirms that Aelin does indeed know the location of at least one Wyrdkey, she demands Aelin tell her, and even tries to compel the information out of Rowan by using the blood oath. However, once it is clear that Aelin has not told Rowan, Fenrys and his twin brother Connall force Rowan to kneel and hold him down as Gavriel and Lorcan whip him in order to coerce Aelin.
When Aelin encompasses Doranelle in flames and frees Rowan from his blood oath, Fenrys and the rest of the cadre seem incredibly shocked, and none of them say good-bye to Rowan and Aelin as they flee Doranelle. Fenrys is not seen again after this until Empire of Storms.
Fenrys first appears in Skull's Bay, when Rowan and Dorian are trying to convince the Pirate Lord Rolfe to aide their cause. Fenrys and Gavriel have been sent to Erilea by Maeve to hunt down and kill Lorcan for his betrayal. They ask Rowan for help regarding tracking Lorcan down, but Rowan refuses, claiming he "washed his hands of [them] all this spring" and does not tell them of Lorcan's whereabouts. However, after Rowan tells Gavriel about his son, both Fenrys and Gavriel agree to help out Aelin and her court.
It is also revealed at this point that Fenrys was the one who originally wanted to train Aelin when Maeve told them all that she had come to Wendlyn. Rowan explains that Fenrys loved anything that was wild and beautiful, and Maeve knew that dangling Aelin in front of him was torture. Fenrys tells Aelin he wanted to train her because it would have gotten him out of Doranelle and away from Maeve - he also claims that they would have had much more fun.
Fenrys is present during the battle at Skull's Bay, and after Deanna possesses Aelin and blows up most of Morath's fleet, Fenrys uses his transporting abilities to retrieve her from the water and get her to a safe place.
After Fenrys is injured during a fight with the ilken on the ships, he tells Aelin about his past and how he came to serve Maeve. His parents were both warriors, and trained his brother and himself to be the same. When they turned thirty, they were straining at the leash to go to Doranelle and meet the queen. However, when they finally went and Maeve asked Fenrys to take the blood oath, he refused. So when Fenrys left to go fight a war with the Akkadians, Maeve offered the blood oath to Connall who, after having spent his entire life living in Fenrys's shadow, agreed.
When Fenrys returned from battle and discovered his brother bound to the queen and found out what he was forced to do behind closed doors, he bargained with Maeve: he would swear the blood oath, but only to take her attention off Connall. Fenrys makes it no secret that he hates both Maeve and the blood oath she forced him to take.
Upon arriving in the Marshes of Ellwye, Fenrys and Gavriel both warn Rowan that Maeve knows Aelin will lead her to the Wyrdkeys and will most likely strike when Aelin is at her weakest. Fenrys has become very attached to Aelin, and tells Rowan to kill him if Maeve ever gives him the order to take her out. Rowan and agrees and Fenrys thanks him, saying he's glad to have been a part of this court, no matter how short a time it may have been.
When Lorcan and Elide arrive in the Marshes after Aelin incinerates the legion of ilken, Fenrys and Gavriel attack him, unable to stop themselves due to the blood oath's command. As Fenrys goes in for the kill, Elide jumps in front of him and Fenrys accidentally hurts Elide instead, ripping out part of her arm and hitting an artery. Gavriel heals her, and although Elide does not blame Fenrys, Aelin was very upset with him, much to his dismay.
When Maeve's armada attack's Aelin's fleet, Fenrys stays to help them, as does Gavriel and Lorcan. However, part way through the battle, the blood oath forces them to return to Maeve and Fenrys transports both of them off the ships. They eventually show up as Maeve and Aelin are fighting, and Fenrys aggressively stands up for Aelin. Maeve acknowledges Fenrys's loyalty to Aelin and mockingly asks if he's enjoyed "playing loyal servant [to her] while panting after the young Queen of Fire."
After realizing that Gavriel and Fenrys found a way out of their order to eliminate Lorcan on site, Maeve breaks the blood oath with Gavriel and claims he is dishonourable and betrayed his queen for another. However, Maeve does not break Fenrys's blood oath, as she is well aware of how much he hates her and figures a better punishment for him should be to serve her forever.
As Aelin is being whipped by Cairn, Fenrys is forced by Maeve to stay where he is and not help her. After Aelin is put into the iron coffin and sent to Maeve's ship, she orders Fenrys to go as well, and he vanishes. When Lorcan and Gavriel tell Rowan they will go with him to get Aelin back, Lorcan says that Fenrys will know they are all coming for her, and try to leave clues if he can. Fenrys cares very deeply for Aelin, treating her like his true Queen, and it is assumed he will do his best to help her while she is held captive by Maeve.
- Fenrys tends to get cranky when he hasn't eaten.