One of the generals of Múspell, the Order of Heroes first encounters her in Chapter 2 of Book 2, fighting alongside her father and Loki. Encountering the Order several times, Surtr eventually orders Laevatein to track and kill them.
In Chapter 5, Laevatein tracks them down, and stating her orders, she fights them. When defeated, Laevatein follows her sister's previous instructions and retreats from the battle. During her escape, she encounters Laegjarn and tells her she's received orders from their father, but appears to grow concerned when her sister expresses unhappiness over the upcoming battles. Nevertheless, she join forces with her, and after the battle with the order, when Laegjarn wonders aloud what to do, Laevatein states that she will set herself ablaze, causing Laegjarn to immediately reject the idea, telling her the flames of Múspell are dangerous and making Laevatein promise she resort to it, which she agrees, but worries over their failure, asking what they should do. Prompting Laegjarn to ask Laevatein in helping her think of a plan.
In Chapter 6, when Laegjarn and Laevatein are lured to a trap by Alfonse and Fjorm, Laevatein panickedly reports that the enemy is coming to their closed off position, causing Laegjarn to instruct Laevatein to escape by herself while Laegjarn keeps them busy. While Laevatein objects, despite Laegjarn's attempts to assure her, Laegjarn tells her it's an order, and Laevatein reluctantly does as she's told, escaping undetected.
In Chapter 13, she is injured by Surtr as punishment for failing to defeat the Order and is almost used as a sacrifice for the Rite of Flames before Laegjarn intervenes and takes her place. She then faces the Order once more as retaliation for Laegjarn's death, and nearly goes through with using the Rite of Flames, but relents when Fjorm reveals that her sister's last wish was for Laevatein to live. In the aftermath, she assumes leadership of Múspell.