Collei is a manga-original character and one of its main characters.
Collei is at first presented in the manga to be slightly cold, and not wanting to deal with or be helped by other people. Later on, with the help of Amber, she starts opening up.
Collei is a bit shorter than Amber, and her appearance details wavy, short, light green hair that goes to her neck with purple eyes that almost touch magenta.
In her first appearance in the manga, she is wearing bandages covering her face to her arm, and she is wearing grey rags and saggy pants, with a grey trapper hat constructed out of bandages.
However, as Cyno seals and puts her Archon residue to a dormant state, she is free from the bandages. As seen in Chapter 16, she is wearing a black shirt which is layered over by a beige messenger's sack, and wearing a black cloak over both. She wears a lime green and yellow bandanna-like belt with black shorts, boots, and socks almost to her knee. She is also wearing a black trapper hat with white fluff inside.
Collei was born a sickly child, so her worried parents brought her to the seer Barnabas, who explained to them that she had been touched by the deev, a supernatural creature. He tells them to give Collei to him in order to save her. However, Barnabas was working with the Fatui — Dottore in particular — and, instead of saving her, turned Collei into a test subject for their Archon Residue experiments.
It is unknown if the Fatui let Collei go or if Collei escaped herself, but she eventually found herself wandering around alone. On account of her sickliness, she was treated poorly wherever she went; she was often abused by passing pedestrians, thrown rocks at, and pushed around. This fueled her hatred of people and gods, and a strong desire for vengeance.
In search of both of a cure for her illness and a means of revenge, Collei traveled to Mondstadt to visit the Mondstadt Library. Upon her arrival, however, she was refused entry out of fear that she was carrying a plague. Desperate and angry, she summons the Archon Residue inside of her to attack a passing carriage — one carrying two Fatui diplomats. A snake of black fire appears, burning the two diplomats until nothing remained, while fifteen others were wounded. This provided enough of a distraction for Collei to slip into Mondstadt unnoticed.
Due to the recent attack, Amber and Kaeya are sent to investigate. While investigating, Amber sees Collei looking at a statue with anger, and questions her on what she is doing out so late at night. Collei is impatient and tries to convince Amber to let her be, but Amber doesn't stop. Collei then lies and tells her she is searching for something, so Amber decides to help her find whatever she is looking for.
While dragging Collei around, Amber decides to fly with Collei and see if she can see what she is looking for. Upon landing, Amber meets Jean, the Acting Grand Master of the Knights of Favonius and Lisa, the librarian of the Knights of Favonius, who invites Amber to share her intel, and then proposing to go to the library. At first, Amber did not want to go for she had no intel on hand, but Collei knew that what she was looking for could be in the library, convincing Amber to go and bring her along.
While Amber suddenly leaves to go look for an important clue and Lisa goes to find Diluc, Collei takes the scroll which describes what she needs for her revenge, but she soon realizes that she can't read the scroll. At that moment, Kaeya appears in front of her and starts questioning her on why she has the scroll, and what she is doing there. Amber comes back from her small adventure and stops Kaeya from questioning Collei any further. Lisa also returns, and Collei hands over the scroll, but not even Lisa can read it.
With their new intel, both Collei and Amber go look for suspicious Fatui devices. At the same time, that was also the day of Ludi Harpastum, so Amber decides to bring Collei to the festival.
During one of the attractions, Collei is chosen as a volunteer, and is enclosed in a wooden box, which causes Collei's memories to resurface and almost lead her to a breakdown. As Amber opens the box, Collei realizes that Mondstadt is not a dangerous place; it is a place where you are free to be happy, to smile, to cry, and be whoever you want to.
Kaeya starts realizing that Collei might be the culprit. He distracts Amber by telling her that they have found other Fatui devices, sending her off and allowing Kaeya to approach Collei. Kaeya brings her to a deserted area of Mondstadt and starts attacking Collei to make her use her powers. She tries her best not to, but she is then taken by the Archon residue and attacks Kaeya. Amber then finds Collei fighting Kaeya and stops the two, taking Collei with her and running away.
Collei thinks that now Amber hates her, but on the contrary, Amber thinks that she is at least trying to right her wrongs. Amber then tells her that they have decoded the papers and can help Collei find what she needs. After they return to Lisa, she tells them that she has contacted her teacher from her time at Sumeru Academia to see if he knows someone who can aid Collei. The one who answers Lisa's call is Cyno, and he takes Collei and Amber to Starsnatch Cliff in the morning to put Collei's Archon Residue in a dormant state, finally allowing her to turn over a new leaf.
However, just as Amber and Collei are happily celebrating, Barnabas finds Collei, and is ready to take her away. Amber refuses to give Collei away and fights Barnabas, while attempting to protect Collei with a shield at the same time. As Collei watched Amber fight, her memories resurfaced once more. Collei, wanting to protect Amber, thrusts herself at Amber when her shield breaks. Collei asks Amber not to protect her anymore, instead focus on fighting Barnabas. Amber, with Collei's encouragement, and a bit of help from Diluc, defeats Barnabas. Right after that, Diluc disguising himself as the perpetrator of the Black Fire Incident, appears on the scene to take the credit for defeating Barnabas. Kaeya, who is in cahoots with him, helps Barnabas' guards apprehend Diluc, thus absolving Collei of the responsibility of killing the two Fatui diplomats.
After recovering, Collei visits Lisa and asks her to learn how to write. She writes a letter to Amber revealing that she will go with Cyno to Sumeru to study. She also apologizes for not being able to say goodbye to Amber personally and thanks her friend for making Mondstadt so fun for her.
- Barnabas tells Collei's parents that she's been touched by the deev. A deev is a particular sort of supernatural entity with disagreeable characteristics.
- There are hints she is claustrophobic.
- Due to the Archon Residue feeding on Collei's negative emotions, when she encounters such a negative emotion, the Archon Residue let Collei have a vision of what would happen if she had control over the Archon Residue and was filled with hate.
- On the Cat's Tail Message Board, one message talks about a "strange girl" that was "wrapped in bandages," referring to Collei.