Leifer is Enna's older brother.
Leifer chose to stay in the Forest with his mother when his younger sister Enna went the city to earn more money. However, when their mother became ill, he asked Enna to return home to help him care for her.
Some time after his mother's death in the spring, Leifer is out helping some neighbors to clear a section of Forest when he finds a mysterious vellum buried in the roots of a lighting-dead fir tree. He learns from the vellum how to sense heat and pull it into a special place inside his chest, transforming it somehow, and sending it back out as fire.
Leifer returns home to find the house empty and the hearth cold. Making sure his sister's not around, he takes out the vellum and practices fire-speaking, setting the hearth ablaze just before Enna walks in. Hastily putting away the vellum, he quietly sidesteps her questions.
However, his behavior is extremely odd: the normally quiet Leifer is fiercely angry at how forest people are treated in the city and for some reason blames their queen, who also happens to be Enna's best friend. That night, while Finn is visiting, Leifer attempts to persuade him to join a rebellion against the royal family that he's trying to get started, ignoring Enna's shocked protests. The heat that constantly surrounds Leifer pressures him to set it free, and when Enna stands in his way, the heat blinds him into forgetting that she's his sister, making him see her only as an obstacle that needs to be dealt with. Unable to control the heat any longer, he sets fire to Enna's skirt. However, as the heat leaves him, so too does the desire to burn and he immediately is horrified at what he's done. He runs away into the Forest, unable to face the fact that he lost control so badly. When he finally returns, he tearfully apologizes to his unmoved sister and reports that he's joined the Bayern army to fight in the war against Tira.
Leifer tells his captain and his king about his special talents and even lights the camp fires at night. But at the first battle, it is clear that Bayern is outnumbered. Until Leifer starts burning the Tiran alive, that is. His flames single-handedly turn the entire battle around and lead Bayern to victory, but it turns out to be too much effort for Leifer. He pulls in so much heat into the special place inside his chest, it can't take it anymore and snaps. The heat leaks into the rest of his body and burns him from the inside out, killing him.
After the battle ends, Enna finds his charred, blackened body and discovers the vellum he was hiding from her. Desperate to know why her brother died in such a way, she reads it and unlocks the ability to sense heat herself. When the army wants to take Leifer's body and bury it with all the respect due a war hero, she declines and has him cremated instead, understanding that he would have preferred to live once again as warm fire rather than be buried in cold earth.
- Although Leifer was born first, his little sister Enna would often figure things out before he did and would teach him.