Sei has black plaited hair and brown eyes. She wears a grey and brown robe with fox fur. She has a fire brand on either sides of her face and on the chest seen when she moves her collar aside. In her dragon form Sei has a red-brown body with white and grey scales, and has white crystal like spines running down her body from her forehead.
Sei is a straight-to-the-point, quick to anger person who enjoys making mean yet humorous jokes about Dominic, who she nicknames "Lowlander". She is quite solemn, angry most of the time, and doesn't often appreciate jokes at her expense. However she has a good heart and will go to any lengths to protect or seek those she cares about, using her powerful fire-magic to her benefit.
The Crown & The Flame
Sei is first introduced as Hex's fire captive, she intends to use Sei's magic to use the cannon against Kenna's army in the siege of Stormholt. When she meets Dominic for the first time, she recognizes the brand on his chest and reveals that his mother was a member of the mountain tribes. During the siege of Stormholt, Dom frees Sei and together they fight the Nevrakis soldiers and assist Kenna Rys to win the war against Luther Nevrakis.
In Book 2, Sei offers to train Dom to control his fire powers. Dom travels to the Blackspine Mountains to learn from Anu Rhuka, Sei's grandfather. Sei and Dom successfully turn into dragons to help Kenna fight in the final battle, but Dom is captured by Hex.
In Book 3, Sei takes her dragon form and assists in rescuing Dom at Aurelia.
Anu is Sei's grandfather. He affectionately calls her "little Sei-Sei". Even though Sei has got problems to show it, it's clear that her grandfather is very important to her. She even lost her will to live when she thought that Hex had captured him.
Playing as Dom allows the player the choice to flirt and romance Sei, but she doesn't respond very well to his advances. It is hinted that Sei has romantic feelings for Dom in Chapter 4, if your player chooses to kiss Sei as a distraction, she will feel happy for a split second before hastily telling Dom off at his bad timing (the kiss). Sei is extremely upset when Dom is captured by Hex near the end of Book 2.
Although she is rude to Dominic, she eventually grows fond of him, but she doesn't show it very well. An example is when after Dom fails his training, Sei goes into the forest to encourage him not to give up, which shows that she cares for him in her own way. Dom can choose to tease her about liking him, which results in her threatening to burn him.
If the player chooses to drink with Sei, Dom and Sei will share a moment together, and Sei will reveal that she accidentally killed someone when she was a younger, more powerful fire-user (someone she cared about, it is possibly implied to be her grandmother) because of her ignorance when using her fire magic. She becomes sad and upset and Dom can choose to comfort her by holding her hand or kissing her.
In Book 3, Chapter 14, Dom can choose to spend some romantic time with Sei. She offers him to give some private training in the forest but plays an ancient tradition called Fal Ignis.
Sei and Anton are childhood friends, they grew up together. Sei even tells Kenna not to hurt him while getting him freed from Hex.
Sei and Kenna don't exactly hit off, but become best friends when Dom is captured by Hex, and they have to work together to rescue him.