Finn is a young man with wild gray-white hair. White is not his natural hair color; it changed suddenly after he experienced stress. Various green and purple tattoos cover every single visible inch of skin (except for his face) on his body, very cleverly hiding the identity of his spirit animal. Among these is a Zhongese symbol, similar to Yin and Yang.
Finn is said to be quiet and wise. He was once a renowned Greencloak warrior, but "has seen too much war," as quoted by Tarik. He is a wise, brave scout and leader, but the "loss" of his spirit animal, Donn, affects him greatly. He is also very determined for Erdas to flourish, as he was willing to sacrifice his life in order for Conor, Rollan, Abeke, and Meilin to get out of Trunswick safely. Near the end of Hunted, during the battle at Glengavin, Finn is able to summon Donn out of passive state, and he is overjoyed.
After the events of Hunted, he decided to stay in Glengavin. He joins the main team once more in The Evertree, where he leads the trek across Stetriol. In the second series, he is one one of the Greencloaks to be infected with a Wyrm parasite.
In the Books
Finn is called a 'Scout' who takes the Four Fallen on a journey to find the Iron Boar of Rumfuss. Near the first few chapters of the book, he helps Meilin bond with Jhi. In a part of the book, he found some people who had a black cat in a cage. They said it was "The baby black panther of the North." Finn seems quite upset at this, which might give the reader a hint of his spirit animal.
After the battle with the Conquerors in Glengavin's garden, Donn finally comes out of passive state and is reunited with Finn.
In The Evertree, Finn travels from Eura to Greenhaven and re-unites with the team. He accompanies the Four Fallen, Dorian, Maya and Kalani on the journey to Stetriol. He is shown to be good friends with Dorian.
When the group was at some docks, Tini was on the ground away from Maya and Donn started to chase him around. Finn scolds his spirit animal and apologizes to Maya, giving a reproachful look to Donn. When Dorian is stung by a stonefish and dies, Finn takes the gruesome job of removing the maps from his body.
In The Return, Finn is one of the Greencloaks infected by the Wyrm parasite that Zerif unleashed. He fought Kirat in Zourtzi while Donn fought Cabaro, and he injured Kirat before Abeke knocked him unconscious.
Donn is Finn's spirit animal. They were close, until Finn's brothers died in a battle with the Conquerors, causing Donn to go into passive form for a very long time. Because of this, their bond was "complicated". The Earl of Trunswick apparently tried to keep Finn in the Howling House at one point in the series. At the end of Hunted, Donn comes out of passive form to save Conor and is reunited with Finn once again. Finn is revealed to be the real "Legend of the North", and he and Donn decide to live in Glengavin.
Meilin and Finn become good friends in Hunted. Meilin was frustrated about her bond with Jhi, and Finn was the one to comfort her, since he knows what it's like to have a "complicated" bond. Because of Finn, Meilin starts to realize that good things can come out of her bond with Jhi.
Dorian and Finn are both senior Greencloaks, and they lead the expedition to Stetriol in The Evertree. They seem to get along well. When Dorian dies after being stung by a stonefish, Finn takes the job of removing the maps from Dorian's body.
- Finn was revealed by Maggie Stiefvater to be based off of Finn McCool, a man from Celtic mythology.
- Finn is an Irish name meaning "fair". The surname Cooley means "hound of Ulster".
- There is a unique item in the game called Finn's Cloak.
- Finn's hair suddenly turning white is a similar phenomenon to the real-life Marie Antoinette syndrome.